Antigen Binding Molecules Targeting SARS-CoV-2

ABSTRACT

The invention provides, in various embodiments, polypeptides that specifically bind to Spike glycoprotein of severe acute respiratory syndrome coronavirus (e.g., SARS-CoV-2-Spike). The invention also provides, in various embodiments, fusion proteins comprising one or more of the polypeptides, polynucleotides encoding the polypeptides, vectors and host cells suitable for expressing the polypeptides, and methods for treating viral infections (e.g., COVID-19).

RELATED APPLICATIONS

This application is a Continuation of International Application No. PCT/US2021/040533, which designated the United States and was filed on Jul. 6, 2021, published in English, which claims the benefit of U.S. Provisional Application No. 63/070,038, filed on Aug. 25, 2020, and U.S. Provisional Application No. 63/048,588, filed on Jul. 6, 2020. The entire teachings of the above applications are incorporated herein by reference. INCORPORATION BY REFERENCE OF MATERIAL IN XML

This application incorporates by reference the Sequence Listing contained in the following eXtensible Markup Language (XML) file being submitted concurrently herewith:

-   -   a) File name: 57081009003_Sequence_Listing_Replacement.xml;         created May 30, 2023, 96,452 Bytes in size.

BACKGROUND

The SARS-Coronavirus-2 (SARS-CoV-2), a novel coronavirus, first caused a cluster of pneumonia cases (COVID-19) in Wuhan, China. As of Mar. 1, 2020, 79,968 patients in China had tested positive for COVID-19, 2,873 deaths had occurred, equivalent to a mortality rate of 3.6% (95% CI 3.5-3.7) (Baud D. et al., Lancet Infect Dis. (2020)). This figure, however, may be an underestimate of the potential threat of COVID-19 in symptomatic patients (Id.).

COVID-19 has been spreading rapidly throughout the world, resulting in a pandemic. The Coronavirus disease (COVID-2019) situation report released from the World Health Organization on Apr. 21, 2020 reported 2,397,216 confirmed infections and 162,956 deaths. Among them, 83,006 new cases and 5,109 deaths were added within the previous 24 hours. Quarantine, isolation, and infection-control measures have been relied on to prevent disease spread, and supportive care for those who become ill (Baden and Rubin, NEngl J Med., (2020)).

SUMMARY

There is a critical need to develop specific antiviral therapeutic agents for preventing transmission of COVID-19 as well as treating COVID-19 patients.

The invention disclosed herein is based, in part, on the discovery that polypeptides of the present invention specifically bind to the Spike glycoprotein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2-Spike). Accordingly, the invention generally relates to compositions (e.g., polypeptides, pharmaceutical compositions) and methods that are useful for reducing Spike (e.g., SARS-CoV-2-Spike) mediated viral entry into a cell.

Provided herein are polypeptides that specifically bind SARS-CoV-2-Spike. In one aspect, the invention provides polypeptides that specifically bind SARS-CoV-2-Spike, wherein the polypeptide comprises a paratope that is identical to the paratope of an antibody selected from:

-   -   a) an antibody comprising SEQ ID NO: 4 and SEQ ID NO: 13;     -   b) an antibody comprising SEQ ID NO: 5 and SEQ ID NO: 13;     -   c) an antibody comprising SEQ ID NO: 6 and SEQ ID NO: 13;     -   d) an antibody comprising SEQ ID NO: 7 and SEQ ID NO: 14;     -   e) an antibody comprising SEQ ID NO: 8 and SEQ ID NO: 15;     -   f) an antibody comprising SEQ ID NO: 9 and SEQ ID NO: 13;     -   g) an antibody comprising SEQ ID NO: 10 and SEQ ID NO: 13;     -   h) an antibody comprising SEQ ID NO: 41 and SEQ ID NO: 13;     -   i) an antibody comprising SEQ ID NO: 42 and SEQ ID NO: 13     -   j) an antibody comprising SEQ ID NO: 43 and SEQ ID NO: 47;     -   k) an antibody comprising SEQ ID NO: 44 and SEQ ID NO: 48; or     -   1) an antibody comprising SEQ ID NO: 45 and SEQ ID NO: 49.

In another aspect, the invention provides a polypeptide that specifically binds SARS-CoV-2-Spike, wherein the polypeptide comprises:

-   -   a) an immunoglobulin heavy chain variable region (VH) comprising         a heavy chain complementarity determining region 1 (HCDR1), a         heavy chain complementarity determining region 2 (HCDR2) and a         heavy chain complementarity determining region 3 (HCDR3) that         are each identical to the HCDR1, HCDR2 and HCDR3, respectively,         of SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ         ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 41, SEQ ID NO:         42, SEQ ID NO: 43, SEQ ID NO: 44 or SEQ ID NO: 45; and     -   b) an immunoglobulin light chain variable region (VL) comprising         a light chain complementarity determining region 1 (LCDR1), a         light chain complementarity determining region 2 (LCDR2) and a         light chain complementarity determining region 3 (LCDR3) that         are each identical to the LCDR1, LCDR2 and LCDR3, respectively,         of SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 47,         SEQ ID NO: 48 or SEQ ID NO: 49.

In some embodiments, the polypeptide comprises the HCDR1, HCDR2 and HCDR3, and LCDR1, LCDR2 and LCDR3, of an antibody selected from:

-   -   a) an antibody comprising SEQ ID NO: 4 and SEQ ID NO: 13;     -   b) an antibody comprising SEQ ID NO: 5 and SEQ ID NO: 13;     -   c) an antibody comprising SEQ ID NO: 6 and SEQ ID NO: 13;     -   d) an antibody comprising SEQ ID NO: 7 and SEQ ID NO: 14;     -   e) an antibody comprising SEQ ID NO: 8 and SEQ ID NO: 15;     -   f) an antibody comprising SEQ ID NO: 9 and SEQ ID NO: 13;     -   g) an antibody comprising SEQ ID NO: 10 and SEQ ID NO: 13;     -   h) an antibody comprising SEQ ID NO: 41 and SEQ ID NO: 13;     -   i) an antibody comprising SEQ ID NO: 42 and SEQ ID NO: 13;     -   j) an antibody comprising SEQ ID NO: 43 and SEQ ID NO: 47;     -   k) an antibody comprising SEQ ID NO: 44 and SEQ ID NO: 48; or     -   l) an antibody comprising SEQ ID NO: 45 and SEQ ID NO: 49.

In some embodiments, the polypeptide further comprises a paratope that is identical to the paratope of an antibody comprising:

-   -   a) SEQ ID NO: 4 and SEQ ID NO: 13;     -   b) SEQ ID NO: 5 and SEQ ID NO: 13;     -   c) SEQ ID NO: 6 and SEQ ID NO: 13;     -   d) SEQ ID NO: 7 and SEQ ID NO: 14;     -   e) SEQ ID NO: 8 and SEQ ID NO: 15;     -   f) SEQ ID NO: 9 and SEQ ID NO: 13;     -   g) SEQ ID NO: 10 and SEQ ID NO: 13;     -   h) SEQ ID NO: 41 and SEQ ID NO: 13;     -   i) SEQ ID NO: 42 and SEQ ID NO: 13;     -   j) an antibody comprising SEQ ID NO: 43 and SEQ ID NO: 47;     -   k) an antibody comprising SEQ ID NO: 44 and SEQ ID NO: 48; or     -   1) an antibody comprising SEQ ID NO: 45 and SEQ ID NO: 49.

In yet another aspect, the invention provides a polypeptide that comprises a VH comprising SEQ ID NO: 2, wherein:

-   -   a) X₁ is not T;     -   b) X₂ is not R;     -   c) X₃ is not S;     -   d) X₄ is not T;     -   e) X₅ is not T;     -   f) X₆ is not L;     -   g) X₇ is not L;     -   h) X₈ is not R;     -   i) X₉ is not T;     -   j) X₁₀ is not L; or     -   k) X₁₁ is not Y,         or any combination of the foregoing.

In some embodiments, the polypeptide further comprises a VL comprising SEQ ID NO: 11, wherein:

-   -   a) X₁₂ is not S;     -   b) X₁₃ is not L; or     -   c) X₁₄ is not V,         or any combination of the foregoing.

In yet another aspect, the invention provides a polypeptide that specifically binds a SARS-CoV-2-Spike, comprising a VH comprising SEQ ID NO: 46, wherein:

-   -   X₁ is E or Q;     -   X₂ is P or S;     -   X₃ is A or E;     -   X₄ is L or V;     -   X₅ is I or V;     -   X₆ is S or T;     -   X₇ is A or M;     -   X₈ is K or Q;     -   X₉ is G or S;     -   X₁₀ is N, Q or R;     -   X₁₁ is A or S;     -   X₁₂ is P or Q;     -   X₁₃ is K or S;     -   X₁₄ is Q or R;     -   X₁₅is L or M;     -   X₁₆ is S or T;     -   X₁₇ is A or V;     -   X₁₈ is K or T;     -   X₁₉ is S or T;     -   X₂₀ is L or M;     -   X₂₁ is E or Q;     -   X₂₂ is L or W;     -   X₂₃ is N or S;     -   X₂₄ is R or S;     -   X₂₅ is K or R;     -   X₂₆ is A or S;     -   X₂₇ is D or S;     -   X₂₈ is M or V;     -   X₂₉ is F or Y;     -   X₃₀ is N or R; or     -   X₃₁ is V or Y,     -   or any combination of the foregoing.

In some embodiments, the polypeptide further comprises a VL comprising SEQ ID NO: 50, wherein:

-   -   X₃₂is D or E;     -   X₃₃ is Q or V;     -   X₃₄ is L or M;     -   X₃₅ is G or S;     -   X₃₆ is S or T;     -   X₃₇ is A or L;     -   X₃₈ is P or V;     -   X₃₉is D or E;     -   X₄₀is A or V;     -   X₄₁ is I or L;     -   X₄₂ is S or T;     -   X₄₃ is E or G;     -   X₄₄ is A, N or S;     -   X₄₅ is L or Y;     -   X₄₆ is E or G;     -   X₄₇ is K or Q;     -   X₄₈ is K or R;     -   X₄₉ is S or T;     -   X₅₀ is A or Q;     -   X₅₁ is S or T;     -   X₅₂ is I or V;     -   X₅₃ is D or S;     -   X₅₄ is R or S;     -   X₅₅ is E or Q;     -   X₅₆ is T or V;     -   X₅₇ is L or Q; or     -   X₅₈ is L or V,     -   or any combination of the foregoing.

In another aspect, the invention provides a polypeptide that specifically binds SARS-CoV-2-Spike, comprising:

-   -   a) a V_(H) sequence that is at least 70% identical to SEQ ID NO:         3;     -   b) a V_(L) sequence that is at least 70% identical to SEQ ID NO:         12; or     -   c) a combination thereof,         wherein the V_(H) sequence does not comprise SEQ ID NO: 3, the         V_(L) sequence does not comprise SEQ ID NO: 12, or both.

In some embodiments, the polypeptides of the invention are fusion proteins.

In other aspects, the invention provides a polynucleotide encoding a polypeptide disclosed herein, a vector comprising such polynucleotide, and a host cell comprising such polynucleotide or vector.

In another aspect, the invention provides a method of treating a subject in need thereof (e.g., a subject having a SARS-CoV infection, such as COVID-19), comprising administering to the subject an effective amount of a polypeptide disclosed herein or a composition (e.g., pharmaceutical composition) comprising a polypeptide disclosed herein.

In another aspect, the invention provides a method of inhibiting fusion between SARS-CoV-2-Spike and a cell (e.g., a cell in a subject), comprising contacting the cell with an effective amount of a composition comprising a polypeptide disclosed herein or a composition (e.g., pharmaceutical composition) comprising a polypeptide disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing will be apparent from the following more particular description of example embodiments, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments.

FIG. 1 depicts the amino acid sequence of the receptor binding domain of SARS-Cov-2-Spike (RBD). The epitope residues bound by the Reference antibody disclosed herein are indicated by asterisks.

FIG. 2A depicts an alignment of non-limiting examples of heavy chain variable (V_(H)) sequences that are useful in polypeptides of the invention. The heavy chain complementarity determining region (HCDR) sequences are indicated using bold letters and underlining. “*” indicates paratope residues. The position of X_(n), where n is a number from 1-11, is indicated by the corresponding numbers at the bottom of the alignment. Also see V_(H) consensus A (SEQ ID NO: 2) in Table 1.

FIG. 2B depicts an alignment of non-limiting examples of light chain variable (V_(L)) sequences that are useful in polypeptides of the invention. The light chain complementarity determining region (LCDR) sequences are indicated using bold text and underlining. “*” indicates paratope residues. The position of X_(n), where n is a number from 12-14, is indicated by the corresponding numbers at the bottom of the alignment. Also see V_(L) consensus A (SEQ ID NO: 11) in Table 1.

FIG. 3A depicts an alignment of non-limiting examples of heavy chain variable (V_(H)) sequences that are useful in polypeptides of the invention. The heavy chain complementarity determining region (HCDR) sequences are indicated using bold letters and underlining. “*” indicates paratope residues. The position of Xn, where n is a number from 1-31, is indicated by the corresponding numbers at the bottom of the alignment. Also see V_(H) consensus B (SEQ ID NO: 46) in Table 1.

FIG. 3B depicts an alignment of non-limiting examples of light chain variable (V_(L)) sequences that are useful in polypeptides of the invention. The light chain complementarity determining region (LCDR) sequences are indicated using bold text and underlining. “*” indicates paratope residues. The position of Xn, where n is a number from 32-58, is indicated by the corresponding numbers at the bottom of the alignment. Also see V_(L) consensus B (SEQ ID NO: 50) in Table 1.

FIG. 4A depicts an alignment of non-limiting examples of heavy chain variable (V_(H)) sequences that are useful in polypeptides of the invention. The heavy chain complementarity determining region (HCDR) sequences are indicated using bold letters and underlining. “*” indicates paratope residues. The position of Xn, where n is a number from 1-55, is indicated by the corresponding numbers at the bottom of the alignment.

FIG. 4B depicts an alignment of non-limiting examples of light chain variable (V_(L)) sequences that are useful in polypeptides of the invention. The light chain complementarity determining region (LCDR) sequences are indicated using bold text and underlining. “*” indicates paratope residues. The position of Xn, where n is a number from 56-94, is indicated by the corresponding numbers at the bottom of the alignment.

FIG. 5 illustrates the ability of a polypeptide of the invention (AB-8, IgG) to neutralize mutant SARS-COV-2 pseudovirus. The bars represent fold-difference (WT-Mutant)/(WT) in IC₅₀ values for antibody neutralization of pseudoviruses bearing emerging mutations or deletions relative to the parent D614G-parent virus. Values between−2.5 and 2.5 are considered as not significant in this assay.

FIG. 6 depicts the affinities of humanized IgG1 antibodies (grey bars) and the seed antibodies (black bars) to COV-2 RBD measured with biolayer interferometry.

FIG. 7 depicts the association and dissociation of the humanized IgG1 antibodies (grey traces) and the seed antibodies (black traces) to COV-2 RBD measured with biolayer interferometry.

DETAILED DESCRIPTION

A description of example embodiments follows.

Several aspects of the invention are described below, with reference to examples for illustrative purposes only. It should be understood that numerous specific details, relationships, and methods are set forth to provide a full understanding of the invention. One having ordinary skill in the relevant art, however, will readily recognize that the invention can be practiced without one or more of the specific details or practiced with other methods, protocols, reagents, cell lines and animals. The invention is not limited by the illustrated ordering of acts or events, as some acts may occur in different orders and/or concurrently with other acts or events. Furthermore, not all illustrated acts, steps or events are required to implement a methodology in accordance with the invention. Many of the techniques and procedures described, or referenced herein, are well understood and commonly employed using conventional methodology by those skilled in the art.

Polypeptides Binding SARS-CoV-2 Spike Protein

SARS-CoV-2 is the causative agent of COVID-19. SARS-CoV-2-Spike, or S protein of the SARS-CoV-2, is a protein that facilitates entry of the SARS-CoV-2 virus into a host cell, such as a human host cell. Without being bound by theory, it is believed SARS-CoV-2-Spike facilitates infection by binding to an entry receptor on the surface of a host cell (e.g., angiotensin converting enzyme 2 (ACE2) or Transmembrane protease, serine 2 (TMPRSS2)). A non-limiting example of a wildtype SARS-CoV-2-Spike sequence is NCBI RefSeq YP_009724390 (SEQ ID NO. 1).

(SEQ ID NO: 1) MFVFLVLLPLVSSQCVNLTTRTQLPPAYTNSFTRGVYYPDKVFRSSVLHS TQDLFLPFFSNVTWFHAIHVSGTNGTKRFDNPVLPFNDGVYFASTEKSNI IRGWIFGTTLDSKTQSLLIVNNATNVVIKVCEFQFCNDPFLGVYYHKNNK SWMESEFRVYSSANNCTFEYVSQPFLMDLEGKQGNFKNLREFVFKNIDGY FKIYSKHTPINLVRDLPQGFSALEPLVDLPIGINITRFQTLLALHRSYLT PGDSSSGWTAGAAAYYVGYLQPRTFLLKYNENGTITDAVDCALDPLSETK CTLKSFTVEKGIYQTSNFRVQPTESIVRFPNITNLCPFGEVFNATRFASV YAWNRKRISNCVADYSVLYNSASFSTFKCYGVSPTKLNDLCFTNVYADSF VIRGDEVRQIAPGQTGKIADYNYKLPDDFTGCVIAWNSNNLDSKVGGNYN YLYRLFRKSNLKPFERDISTEIYQAGSTPCNGVEGFNCYFPLQSYGFQPT NGVGYQPYRVVVLSFELLHAPATVCGPKKSTNLVKNKCVNFNFNGLTGTG VLTESNKKFLPFQQFGRDIADTTDAVRDPQTLEILDITPCSFGGVSVITP GTNTSNQVAVLYQDVNCTEVPVAIHADQLTPTWRVYSTGSNVFQTRAGCL IGAEHVNNSYECDIPIGAGICASYQTQTNSPRRARSVASQSIIAYTMSLG AENSVAYSNNSIAIPTNFTISVTTEILPVSMTKTSVDCTMYICGDSTECS NLLLQYGSFCTQLNRALTGIAVEQDKNTQEVFAQVKQIYKTPPIKDFGGF NFSQILPDPSKPSKRSFIEDLLFNKVTLADAGFIKQYGDCLGDIAARDLI CAQKFNGLTVLPPLLTDEMIAQYTSALLAGTITSGWTFGAGAALQIPFAM QMAYRFNGIGVTQNVLYENQKLIANQFNSAIGKIQDSLSSTASALGKLQD VVNQNAQALNTLVKQLSSNFGAISSVLNDILSRLDKVEAEVQIDRLITGR LQSLQTYVTQQLIRAAEIRASANLAATKMSECVLGQSKRVDFCGKGYHLM SFPQSAPHGVVFLHVTYVPAQEKNFTTAPAICHDGKAHFPREGVFVSNGT HWFVTQRNFYEPQUITTDNTFVSGNCDVVIGIVNNTVYDPLQPELDSFKE ELDKYFKNHTSPDVDLGDISGINASVVNIQKEIDRLNEVAKNLNESLIDL QELGKYEQYIKWPWYIWLGFIAGLIAIVMVTIMLCCMTSCCSCLKGCCSC GSCCKFDEDDSEPVLKGVKLHYT.

As used herein, SARS-CoV-2 Spike includes wild-type SARS-CoV-2 Spike proteins (e.g., SEQ ID NO: 1), variants of wild-type SARS-CoV-2 Spike proteins, and modified forms of wild-type and variant SARS-CoV-2 Spike proteins.

In one aspect, the invention provides a polypeptide that binds to a SARS-CoV-2 Spike protein comprising SEQ ID NO: 1.

In some embodiments, the polypeptide binds to a variant of SARS-CoV-2-Spike. In some embodiments, the variant comprises an amino acid sequence that has at least about 90% sequence identity to the wildtype SARS-CoV-2-Spike sequence (e.g., SEQ ID NO: 1), for example, having at least about: 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, or 99.9% sequence identity to the wildtype SARS-CoV-2-Spike sequence. In some embodiments, the sequence identity is about: 90-99.9%, 90-99.8%, 92-99.8%, 92-99.6%, 94-99.6%, 94-99.5%, 95-99.5%, 95-99.4%, 96-99.4%, 96-99.2%, 97-99.2% or 97-99%.

In some embodiments, the variant SARS-CoV-2-Spike comprises, relative to SEQ ID NO:1, one or more mutations selected from: L5F, S13I, T19R, A67V, 69de1, 70del, D80G, T95I, G142D, 144de1, W152C, E154K, F157S, A222V, D253G, G261D, V367F, K417N, N439K, L452R, Y453F, S477N, E484K, F486L, S494P, E484Q, N501T, N501Y, F565L, A570D, D614G, Q677H, P681H, P681R, A701V, T716I, T859N, F888L, S982A, D950N, Q957R, Q1071H, VI 176F, D1118H, K1 191N, or a combination thereof, e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, orall 45.

In some embodiments, the variant SARS-CoV-2-Spike comprises, relative to SEQ ID NO:1, one or more mutations selected from: 69de1, 70del, 144de1, E484K, S494P, N501Y, A570D, D614G, P681H, T716I, S982A, D1118H or K1 191N, or a combination thereof. In some embodiments, the variant SARS-CoV-2-Spike comprises 69de1, 70del, 144de1, N501Y, A570D, D614G, P681H, T716I, S982A, and D1118H. In some embodiments, the variant SARS-CoV-2-Spike further comprises E484K, S494P or K1191N, or a combination thereof.

In some embodiments, the variant SARS-CoV-2-Spike comprises, relative to SEQ ID NO:1, one or more mutations selected from: D80A, D215G, 241de1, 242de1, 243de1, K417N, E484K, N501Y, D614G or A701V, or a combination thereof. In some embodiments, the variant SARS-CoV-2-Spike comprises D80A, D215G, 241de1, 242de1, 243de1, K417N, E484K, N501Y, D614G, and A701V.

In some embodiments, the variant SARS-CoV-2-Spike comprises, relative to SEQ ID NO:1, one or more mutations selected from: T19R, G142D, 156de1, 157de1, R158G, L452R, T478K, D614G, P681R or D950N, or a combination thereof. In some embodiments, the variant SARS-CoV-2-Spike comprises T19R, 156de1, 157de1, R158G, L452R, T478K, D614G, P681R, and D950N. In some embodiments, the variant SARS-CoV-2-Spike further comprises G142D.

In some embodiments, the variant SARS-CoV-2-Spike comprises, relative to SEQ ID NO:1, one or more mutations selected from: 69de1, 70del, 144de1, A222V, G261D, V367F, K417N, N439K, Y453F, S477N, E484K, F486L, N501T, N501Y, A570D or D614G, or a combination thereof.

In some embodiments, the variant SARS-CoV-2-Spike comprises, relative to SEQ ID NO:1, one or more mutations selected from: E484K, N501Y or D614G, or a combination thereof.

In some embodiments, the modified SARS-CoV-2 Spike protein comprises, relative to SEQ ID NO:1, one or more mutations selected from: F817P, A892P, A899P, A942P, K986P, V987P.

In some embodiments, the polypeptide binds the SARS-CoV-2 Spike protein receptor-binding domain (RBD) (SEQ ID NO: 52) or an epitope within RBD (e.g., RBD 5 (FIG. 1 )).

(SEQ ID NO: 52) RVQPTESIVRFPNITNLCPFGEVFNATRFASVYAWNRKRISNCVADYSVL YNSASFSTFKCYGVSPTKLNDLCFTNVYADSFVIRGDEVRQIAPGQTGKI ADYNYKLPDDFTGCVIAWNSNNLDSKVGGNYNYLYRLFRKSNLKPFERDI STEIYQAGSTPCNGVEGFNCYFPLQSYGFQPTNGVGYQPYRVVVLSFELL HAPATVCGP.

In some embodiments, the polypeptide binds to a variant of the RBD or an epitope within the RBD. In some embodiments, the variant comprises an amino acid sequence that has at least about 90% sequence identity to the wildtype RBD (e.g., SEQ ID NO: 52) or the wildtype RBD 5 (FIG. 1 ), for example, having at least about: 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, or 99.9% sequence identity. In some embodiments, the sequence identity is about: 90-99.9%, 90-99.8%, 92-99.8%, 92-99.6%, 94-99.6%, 94-99.5%, 95-99.5%, 95-99.4%, 96-99.4%, 96-99.2%, 97-99.2% or 97-99%.

In some embodiments, the polypeptide that binds to an SARS-CoV-2 Spike protein (e.g., SEQ ID NO: 1 or SEQ ID NO: 52) and comprises an immunoglobulin light chain variable region, an immunoglobulin heavy chain variable region, or an immunoglobulin light chain variable region and an immunoglobulin heavy chain variable region, wherein the polypeptide does not comprise all five of SEQ ID NO: 17, SEQ ID NO: 21, SEQ ID NO: 24, SEQ ID NO: 31 and SEQ ID NO: 35. In some embodiments, the polypeptide comprises 1, 2, 3 or 4 CDRs selected from SEQ ID NO: 17, SEQ ID NO: 21, SEQ ID NO: 24, SEQ ID NO: 31 and SEQ ID NO: 35.

In another aspect, the invention provides a polypeptide that specifically binds an SARS-CoV-2 Spike protein, wherein the polypeptide comprises:

-   -   a) an immunoglobulin heavy chain variable region (V_(H))         comprising an amino acid sequence that is at least 55% (e.g., at         least 60, 65, 70, 75, 80, 85, 90, 95, 98, or 99%) identical to         SEQ ID NO: 4;     -   b) an immunoglobulin light chain variable region (V_(L))         comprising an amino acid sequence that is at least 55% (e.g., at         least 60, 65, 70, 75, 80, 85, 90, 95, 98, or 99%) identical to         SEQ ID NO: 55; or     -   c) both a) and b),         wherein the polypeptide does not comprise all five of SEQ ID NO:         17, SEQ ID NO: 21, SEQ ID NO: 24, SEQ ID NO: 31 and SEQ ID         NO: 35. In some embodiments, the polypeptide comprises 1, 2, 3         or 4 CDRs selected from SEQ ID NO: 17, SEQ ID NO: 21, SEQ ID NO:         24, SEQ ID NO: 31 and SEQ ID NO: 35.

In some embodiments, the polypeptide binds to a wildtype SARS-CoV-2 Spike protein (e.g., SEQ ID NO:1). In some embodiments, the polypeptide binds to one or more epitope residues of a wildtype SARS-CoV-2 Spike protein (e.g., one or more epitope residues).

As used herein, the term “reference” or “reference polypeptide” refers to a polypeptide (e.g., immunoglobulin molecule) that specifically binds to SARS-CoV-1, and is not a polypeptide of the invention. The sequence of a reference polypeptide and a polypeptide of the invention may be compared to illustrate structural differences between them (e.g., differences at one or more amino acid positions, such as amino acid substitutions). In some embodiments, a polypeptide of the invention will have more than insubstantial differences (e.g., one or more substantial differences) in comparison to a reference polypeptide, such that, generally, polypeptides of the invention will, under controlled conditions, exhibit one or more (i.e., one, two, or all three) of: a different function, in a different way, to achieve a different result, in comparison to a reference polypeptide. Reference polypeptides will vary by one or more amino acids from a polypeptide of the invention, e.g., in some embodiments by 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acids. In certain embodiments, a reference polypeptide diverges from a polypeptide provided by the invention by at least about: 0.4, 0.8, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55% or more amino acid identity.

As used herein, the term “sequence identity,” refers to the extent to which two nucleotide sequences, or two amino acid sequences, have the same residues at the same positions when the sequences are aligned to achieve a maximal level of identity, expressed as a percentage. For sequence alignment and comparison, typically one sequence is designated as a reference sequence, to which a test sequences are compared. The sequence identity between reference and test sequences is expressed as the percentage of positions across the entire length of the reference sequence where the reference and test sequences share the same nucleotide or amino acid upon alignment of the reference and test sequences to achieve a maximal level of identity. As an example, two sequences are considered to have 70% sequence identity when, upon alignment to achieve a maximal level of identity, the test sequence has the same nucleotide or amino acid residue at 70% of the same positions over the entire length of the reference sequence.

Alignment of sequences for comparison to achieve maximal levels of identity can be readily performed by a person of ordinary skill in the art using an appropriate alignment method or algorithm. In some instances, the alignment can include introduced gaps to provide for the maximal level of identity. Examples include the local homology algorithm of Smith & Waterman, Adv. Appl. Math. 2:482 (1981), the homology alignment algorithm of Needleman & Wunsch, J. Mol. Biol. 48:443 (1970), the search for similarity method of Pearson & Lipman, Proc. Nat'l. Acad. Sci. USA 85:2444 (1988), computerized implementations of these algorithms (GAP, BESTFIT, FASTA, and TFASTA in the Wisconsin Genetics Software Package, Genetics Computer Group, 575 Science Dr., Madison, Wis.), and visual inspection (see generally Ausubel et al., Current Protocols in Molecular Biology).

When using a sequence comparison algorithm, test and reference sequences are input into a computer, subsequent coordinates are designated, if necessary, and sequence algorithm program parameters are designated. The sequence comparison algorithm then calculates the percent sequence identity for the test sequence(s) relative to the reference sequence, based on the designated program parameters. A commonly used tool for determining percent sequence identity is Protein Basic Local Alignment Search Tool (BLASTP) available through National Center for Biotechnology Information, National Library of Medicine, of the United States National Institutes of Health. (Altschul et al., 1990).

The term “polypeptide” “peptide” or “protein” denotes a polymer of at least two amino acids covalently linked by an amide bond, regardless of length or post-translational modification (e.g., glycosylation or phosphorylation). A protein, peptide or polypeptide can comprise any suitable L-and/or D-amino acid, for example, common α-amino acids (e.g., alanine, glycine, valine), non-α-amino acids (e.g., β-alanine, 4-aminobutyric acid, 6-aminocaproic acid, sarcosine, statine), and unusual amino acids (e.g., citrulline, homocitruline, homoserine, norleucine, norvaline, ornithine). The amino, carboxyl and/or other functional groups on a peptide can be free (e.g., unmodified) or protected with a suitable protecting group. Suitable protecting groups for amino and carboxyl groups, and methods for adding or removing protecting groups are known in the art and are disclosed in, for example, Green and Wuts, “Protecting Groups in Organic Synthesis,” John Wiley and Sons, 1991. The functional groups of a protein, peptide or polypeptide can also be derivatized (e.g., alkylated) or labeled (e.g., with a detectable label, such as a fluorogen or a hapten) using methods known in the art. A protein, peptide or polypeptide can comprise one or more modifications (e.g., amino acid linkers, acylation, acetylation, amidation, methylation, terminal modifiers (e.g., cyclizing modifications), N-methyl-α-amino group substitution), if desired. In addition, a protein, peptide or polypeptide can be an analog of a known and/or naturally-occurring peptide, for example, a peptide analog having conservative amino acid residue substitution(s).

In one aspect, the invention provides a polypeptide that specifically binds SARS-CoV-2-Spike, wherein the polypeptide comprises a paratope that is identical to the paratope of an antibody selected from:

-   -   a) an antibody comprising SEQ ID NO: 4 and SEQ ID NO: 13;     -   b) an antibody comprising SEQ ID NO: 5 and SEQ ID NO: 13;     -   c) an antibody comprising SEQ ID NO: 6 and SEQ ID NO: 13;     -   d) an antibody comprising SEQ ID NO: 7 and SEQ ID NO: 14;     -   e) an antibody comprising SEQ ID NO: 8 and SEQ ID NO: 15;     -   f) an antibody comprising SEQ ID NO: 9 and SEQ ID NO: 13;     -   g) an antibody comprising SEQ ID NO: 10 and SEQ ID NO: 13;     -   h) an antibody comprising SEQ ID NO: 41 and SEQ ID NO: 13;     -   i) an antibody comprising SEQ ID NO: 42 and SEQ ID NO: 13;     -   j) an antibody comprising SEQ ID NO: 43 and SEQ ID NO: 47;     -   k) an antibody comprising SEQ ID NO: 44 and SEQ ID NO: 48; or     -   l) an antibody comprising SEQ ID NO: 45 and SEQ ID NO: 49.

See Table 1 for SEQ ID NOs: 4-10, 13-15, 41-45, and 47-49 and FIGS. 2A-4B for the paratope residues of antibodies comprising SEQ ID NOs: 4-10, 13-15, 41-45, and 47-49.

The term “paratope” refers to a set of amino acid residues in an antibody or an antigen-binding fragment thereof that contribute to a binding interaction with an epitope of a target protein. The binding interaction can be a hydrogen bond, a salt bridge, a van der Waal interaction, an ionic bond or a combination thereof. A binding interaction may be direct, or indirect, e.g., via a coordinated intermediate molecule, such as an ion or water. The residues of a paratope, in some embodiments, comprise only residues that are part of a defined CDR. In other embodiments, the residues of a paratope further comprise one or more residues that are not part of a defined CDR.

In some embodiments, the paratope is oriented less than about 5.0 angstroms from an epitope on a target antigen when the polypeptide is bound to the target antigen, e.g., less than about: 4.5, 4.0, 3.5, 3.0, 2.5, 2.4, 2.3, 2.2, 2.1, 2.0, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, 1.0 or 0.9 angstroms, or about: 0.9-5.0, 0.9-4.8, 1.0-5, 1.0-4.5, 1.0-4.0, 1.0-3.5, 1.1-3.5, 1.1-3.0, 1.2-3.0, 1.2-2.5, 1.3-2.5, 1.3-2.4, 1.4-2.4, 1.4-2.3, 1.5-2.3, 1.5-2.2, 1.6-2.2, 1.6-2.1, 1.7-2.1, 1.7-2.0 or 1.8-2.0 angstroms, from the epitope. In some embodiments, all of the amino acid residues constituting the paratope are oriented less than about 5.0 angstroms from an epitope on a target antigen when the polypeptide is bound to the target antigen. In other embodiments, less than all of the amino acid residues constituting the paratope (e.g., about 40%, 50%, 60%, 70%, 80%, 90% of the amino acid residues) in the paratope are oriented less than about 5.0 angstroms from an epitope on a target antigen when the polypeptide is bound to the target antigen.

In some embodiments, the polypeptide comprising a paratope disclosed herein comprises an immunoglobulin heavy chain variable region (V_(H)) and an immunoglobulin light chain variable region (V_(L)). In certain embodiments, the paratope residues are contained within the V_(H) and V_(L) of the polypeptide.

In another aspect, the invention provides a polypeptide that specifically binds SARS-CoV-2-Spike, wherein the polypeptide comprises:

-   -   a) a V_(H) comprising an HCDR1, an HCDR2 and an HCDR3 that are         each identical to the HCDR1, HCDR2 and HCDR3, respectively, of         SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID         NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 41, SEQ ID NO:         42, SEQ ID NO: 43, SEQ ID NO: 44 or SEQ ID NO: 45; and     -   b) a V_(L) comprising a LCDR1, a LCDR2 and a LCDR3 that are each         identical to the LCDR1, LCDR2 and LCDR3, respectively, of SEQ ID         NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 47, SEQ ID NO:         48 or SEQ ID NO: 49.

In some embodiments, the polypeptide comprises the HCDR1, HCDR2 and HCDR3, and LCDR1, LCDR2 and LCDR3, of an antibody selected from:

-   -   a) an antibody comprising SEQ ID NO: 4 and SEQ ID NO: 13;     -   b) an antibody comprising SEQ ID NO: 5 and SEQ ID NO: 13;     -   c) an antibody comprising SEQ ID NO: 6 and SEQ ID NO: 13;     -   d) an antibody comprising SEQ ID NO: 7 and SEQ ID NO: 14;     -   e) an antibody comprising SEQ ID NO: 8 and SEQ ID NO: 15;     -   f) an antibody comprising SEQ ID NO: 9 and SEQ ID NO: 13;     -   g) an antibody comprising SEQ ID NO: 10 and SEQ ID NO: 13;     -   h) an antibody comprising SEQ ID NO: 41 and SEQ ID NO: 13;     -   i) an antibody comprising SEQ ID NO: 42 and SEQ ID NO: 13;     -   j) an antibody comprising SEQ ID NO: 43 and SEQ ID NO: 47;     -   k) an antibody comprising SEQ ID NO: 44 and SEQ ID NO: 48; or     -   l) an antibody comprising SEQ ID NO: 45 and SEQ ID NO: 49.

The CDR (e.g., HCDR1, HCDR2, HCDR3, LCDR1, LCDR2 and/or LCDR3) can be a CDR defined by any art-recognized method for identifying CDR residues of an antibody, as described further herein (e.g., a CDR as defined by Kabat, a CDR as defined by Chothia).

In some embodiments, the polypeptide further comprises a paratope that is identical to the paratope of an antibody comprising:

-   -   a) SEQ ID NO: 4 and SEQ ID NO: 13;     -   b) SEQ ID NO: 5 and SEQ ID NO: 13;     -   c) SEQ ID NO: 6 and SEQ ID NO: 13;     -   d) SEQ ID NO: 7 and SEQ ID NO: 14;     -   e) SEQ ID NO: 8 and SEQ ID NO: 15;     -   f) SEQ ID NO: 9 and SEQ ID NO: 13;     -   g) SEQ ID NO: 10 and SEQ ID NO: 13;     -   h) SEQ ID NO: 41 and SEQ ID NO: 13;     -   i) SEQ ID NO: 42 and SEQ ID NO: 13;     -   j) SEQ ID NO: 43 and SEQ ID NO: 47;     -   k) SEQ ID NO: 44 and SEQ ID NO: 48; or     -   l) SEQ ID NO: 45 and SEQ ID NO: 49.

In another aspect, the invention provides a polypeptide that specifically binds SARS-CoV-2-Spike, comprising a V_(H) comprising SEQ ID NO: 2, wherein:

-   -   a) X₁ is not T;     -   b) X₂ is not R;     -   c) X₃ is not S;     -   d) X₄ is not T;     -   e) X₅ is not T;     -   f) X₆ is not L;     -   g) X₇ is not L;     -   h) X₈ is not R;     -   i) X₉ is not T;     -   j) X₁₀ is not L; or     -   k) X₁₁ is not Y,         or any combination of the foregoing.

The sequence identified as SEQ ID NO: 2 is shown below, which is a consensus V_(H) sequence for SEQ ID Nos: 3-10 herein.

(SEQ ID NO: 2) EVQLEESGTVLARPGASVKMSCKASGYTFTX₁YX₂MHWIKQRPGQGLEWI GAIYPGNX₃DTX₄YNQKFKDKAKLTAVX₅STSSAYMELSSLTNEDSAVYF CTREGIPQX₆X₇X₈X₉X₁₀DX₁₁WGQGTSVTVSS.

In some embodiments, the polypeptides disclosed herein further comprise a V_(L). In some embodiments, the polypeptide comprises a V_(L) comprising SEQ ID NO: 11, wherein:

-   -   a) X₁₂ is not S;     -   b) X₁₃ is not L; or     -   c) X₁₄ is not V,         or any combination of the foregoing.

The sequence identified as SEQ ID NO: 11 is shown below, which is a consensus V_(L) sequence for SEQ ID Nos: 12-15 herein:

(SEQ ID NO: 11) DILMTQSPSSLSASLGERVSLTCRASQEIX₁₂GYLSWLQEKPDGTIKRLI YAASTLDSGVPKRFSGSRSGSDYSLTISSLESEDFADYYCX₁₃QYX₁₄SY PWTFGGGTKLEIK.

In some embodiments:

-   -   a) X₁ is T or S;     -   b) X₂is R or W;     -   c) X₃ is S or G;     -   d) X₄ is T, Q or N;     -   e) X₅ is T or K;     -   f) X₆ is L or K;     -   g) X₇ is L or T;     -   h) X₈ is R or N;     -   i) X₉ is T or S;     -   j) X₁₀ is L or F; or     -   k) X₁₁ is Y or V,         or any combination of the foregoing.

In some embodiments:

-   -   a) X₁ is S;     -   b) X₂ is W;     -   c) X₃ is G;     -   d) X₄ is Q or N;     -   e) X₅ is K;     -   f) X₆ is K;     -   g) X₇ is T;     -   h) X₈ is N;     -   i) X₉ is S;     -   j) X₁₀ is F; or     -   k) X₁₁ is V,         or any combination of the foregoing.

In some embodiments, X1 is not T. In some embodiments, X1 is T or S. In some embodiments, X₁ is T. In some embodiments, X1 is S. In some embodiments, X₂ is not R. In some embodiments, X₂ is R or W. In some embodiments, X₂ is R. In some embodiments, X₂ is W. In some embodiments, X₃ is not S. In some embodiments, X₃ is S or G. In some embodiments, X₃ is S. In some embodiments, X₃ is G. In some embodiments, X₄ is not T. In some embodiments, X₄ is T, Q or N. In some embodiments, X₄ is T. In some embodiments, X₄ is Q. In some embodiments, X₄ is N. In some embodiments, X₅ is not T. In some embodiments, X₅ is T or K. In some embodiments, X₅ is T. In some embodiments, X₅ is K. In some embodiments, X₆ is not L. In some embodiments, X₆ is L or K. In some embodiments, X₆ is L. In some embodiments, X₆ is K. In some embodiments, X₇ is not L. In some embodiments, X₇ is L or T. In some embodiments, X₇ is L. In some embodiments, X₇ is T. In some embodiments, X₈ is not R. In some embodiments, X₈ is R or N. In some embodiments, X₈ is R. In some embodiments, X₈ is N. In some embodiments, X₉ is not T. In some embodiments, X₉ is T or S. In some embodiments, X₉ is T. In some embodiments, X₉ is S. In some embodiments, X₁₀ is not L. In some embodiments, X₁₀ is L or F. In some embodiments, X₁₀ is L. In some embodiments, X₁₀ is F. In some embodiments, X₁₁ is not Y. In some embodiments, X₁₁ is Y or V. In some embodiments, X₁₁ is Y. In some embodiments, X₁₁ is V.

In some embodiments:

-   -   a) X₁₂ is S or G;     -   b) X₁₃ is L or Q; or     -   c) X₁₄ is V or L,         or any combination of the foregoing.

In some embodiments:

-   -   a) X₁₂ is G;     -   b) X₁₃ is Q; or     -   c) X₁₄ is L,         or any combination of the foregoing.

In some embodiments, X₁₂ is not S. In some embodiments, X₁₂ is S or G. In some embodiments, X₁₂ is S. In some embodiments, X₁₂ is G. In some embodiments, X₁₃ is not L. In some embodiments, X₁₃ is L or Q. In some embodiments, X₁₃ is L. In some embodiments, X₁₃ is Q. In some embodiments, X₁₄ is not V. In some embodiments, X₁₄ is V or L. In some embodiments, X₁₄ is V. In some embodiments, X₁₄ is L.

In another aspect, the invention provides a polypeptide that specifically binds SARS-CoV-2-Spike, comprising a V_(H) comprising SEQ ID NO: 46, wherein:

-   -   X1 is E or Q;     -   X₂ is P or S;     -   X₃ is A or E;     -   X₄ is L or V;     -   X₅ is I or V;     -   X₆ is S or T;     -   X₇ is A or M;     -   X₈ is K or Q;     -   X₉ is G or S;     -   X₁₀ is N, Q or R;     -   X₁₁ is A or S;     -   X₁₂ is P or Q;     -   X₁₃ is K or S;     -   X₁₄is Q or R;     -   X₁₅ is L or M;     -   X₁₆ is S or T;     -   X₁₇ is A or V;     -   X₁₈ is K or T;     -   X₁₉ is S or T;     -   X₂₀ is L or M;     -   X₂₁ is E or Q;     -   X₂₂ is L or W;     -   X₂₃ is N or S;     -   X₂₄ is R or S;     -   X₂₅ is K or R;     -   X₂₆ is A or S;     -   X₂₇ is D or S;     -   X₂₈ is M or V;     -   X₂₉ is F or Y;     -   X₃₀ is N or R; or     -   X₃₁ is V or Y,     -   or any combination of the foregoing.

The sequence identified as SEQ ID NO: 46 is shown below, which is a consensus V_(H) sequence for SEQ ID Nos: 43-45 herein.

(SEQ ID NO: 46) X₁VQLVQSGAEVKKX₂GX₃SX₄KX₅SCKASGYTFTX₆YWMHWVRQX₇PG X₈GLEWMGAIYPGNX₉DTX₁₀YX₁₁X₁₂X₁₃FQGX₁₄VTX₁₅X₁₆X₁₇D X₁₈SIX₁₉TAYX₂₀X₂₁X₂₂X₂₃X₂₄LX₂₅X₂₆X₂₇DTAX₂₈YX₂₉CTR EGIPQLLX₃₀TLDX₃₁WGQGTLVTVSS.

In some embodiments, X₁ is E or Q. In some embodiments, X₁ is E. In some embodiments, X₁ is Q. In some embodiments, X₂ is P or S. In some embodiments, X₂ is P. In some embodiments, X₂ is S. In some embodiments, X₃ is A or E. In some embodiments, X₃ is A. In some embodiments, X₃ is E. In some embodiments, X₄ is L or V. In some embodiments, X₄ is L. In some embodiments, X₄ is V. In some embodiments, X₅ is I or V. In some embodiments, X₅ is I. In some embodiments, X₅ is V. In some embodiments, X₆ is S or T. In some embodiments, X₆ is S. In some embodiments, X₆ is T. In some embodiments, X₇ is A or M. In some embodiments, X₇ is A. In some embodiments, X₇ is M. In some embodiments, X₈ is K or Q. In some embodiments, X₈ is K. In some embodiments, X₈ is Q. In some embodiments, X₉ is G or S. In some embodiments, X₉ is G. In some embodiments, X₉ is S. In some embodiments, X₁₀ is N, Q or R. In some embodiments, X₁₀ is N. In some embodiments, X₁₀ is Q. In some embodiments, X₁₀ is R. In some embodiments, X₁₁ is A or S. In some embodiments, X₁₁ is A. In some embodiments, X₁₁ is S. In some embodiments, X₁₂ is P or Q. In some embodiments, X₁₂ is P. In some embodiments, X₁₂ is Q. In some embodiments, X₁₃ is K or S. In some embodiments, X₁₃ is K. In some embodiments, X₁₃ is S. In some embodiments, X₁₄ is Q or R. In some embodiments, X₁₄ is Q. In some embodiments, X₁₄ is R. In some embodiments, X₁₅ is L or M. In some embodiments, X₁₅ is L. In some embodiments, X₁₅ is M. In some embodiments, X₁₆ is S or T. In some embodiments, X₁₆ is S. In some embodiments, X₁₆ is T. In some embodiments, X₁₇ is A or V. In some embodiments, X₁₇ is A. In some embodiments, X₁₇ is V. In some embodiments, Xis is K or T. In some embodiments, Xis is K. In some embodiments, Xis is T. In some embodiments, X₁₉ is S or T. In some embodiments, X₁₉ is S. In some embodiments, X₁₉ is T. In some embodiments, X₂₀ is L or M. In some embodiments, X₂₀ is L. In some embodiments, X₂₀ is M. In some embodiments, X₂₁ is E or Q. In some embodiments, X₂₁ is E. In some embodiments, X₂₁ is Q. In some embodiments, X₂₂ is L or W. In some embodiments, X₂₂ is L. In some embodiments, X₂₂ is W. In some embodiments, X₂₃ is N or S. In some embodiments, X₂₃ is N. In some embodiments, X₂₃ is S. In some embodiments, X₂₄ is R or S. In some embodiments, X₂₄ is R. In some embodiments, X₂₄ is S. In some embodiments, X₂₅ is K or R. In some embodiments, X₂₅ is K. In some embodiments, X₂₅ is R. In some embodiments, X₂₆ is A or S. In some embodiments, X₂₆ is A. In some embodiments, X₂₆ is S. In some embodiments, X₂₇ is D or S. In some embodiments, X₂₇ is D. In some embodiments, X₂₇ is S. In some embodiments, X₂₈ is M or V. In some embodiments, X₂₈ is M. In some embodiments, X₂₈ is V. In some embodiments, X₂₉ is F or Y. In some embodiments, X₂₉ is F. In some embodiments, X₂₉ is Y. In some embodiments, X₃₀ is N or R. In some embodiments, X₃₀ is N. In some embodiments, X₃₀ is R. In some embodiments, X₃₁ is V or Y. In some embodiments, X₃₁ is V. In some embodiments, X₃₁ is Y.

In some embodiments, the polypeptides disclosed herein further comprise a V_(L). In some embodiments, the polypeptide comprises a V_(L) comprising SEQ ID NO: 50, wherein:

-   -   X₃₂is D or E;     -   X₃₃ is Q or V;     -   X₃₄ is L or M;     -   X₃₅ is G or S;     -   X₃₆ is S or T;     -   X₃₇ is A or L;     -   X₃₈ is P or V;     -   X₃₉is D or E;     -   X₄₀ is A or V;     -   X₄₁ is I or L;     -   X₄₂ is S or T;     -   X₄₃ is E or G;     -   X₄₄ is A, N or S;     -   X₄₅ is L or Y;     -   X₄₆ is E or G;     -   X₄₇ is K or Q;     -   X₄₈ is K or R;     -   X₄₉ is S or T;     -   X₅₀ is A or Q;     -   X₅₁ is S or T;     -   X₅₂ is I or V;     -   X₅₃ is D or S;     -   X₅₄ is R or S;     -   X₅₅ is E or Q;     -   X₅₆ is T or V;     -   X₅₇ is L or Q; or     -   X₅₈ is L or V,     -   or any combination of the foregoing.

The sequence identified as SEQ ID NO: 50 is shown below, which is a consensus V_(L) sequence for SEQ ID Nos: 47-49 herein:

X₃₂IX₃₃X₃₄TQSPX₃₅X₃₆LSX₃₇SX₃₈GX₃₉RX₄₀TX₄₁X₄₂CRASQX₄₃ISGYLX₄₄WX₄₅Q QKPX₄₆X₄₇APX₄₈RLIYAASX₄₉LX₅₀X₅₁GX₅₂PX₅₃RFSGSGSGTDFTLTISX₅₄LX₅₅PEDFAX₅₆Y YCX₅₇QYLSYPWTFGQGTKX₅₈EIK (SEQ ID NO: 50).In some embodiments, X₃₂ is D or E. In some embodiments, X₃₂ is D. In some embodiments, X₃₂ is E. In some embodiments, X₃₃ is Q or V. In some embodiments, X₃₃ is Q. In some embodiments, X₃₃ is V. In some embodiments, X₃₄ is L or M. In some embodiments, X₃₄ is L. In some embodiments, X₃₄ is M. In some embodiments, X₃₅ is G or S. In some embodiments, X₃₅ is G. In some embodiments, X₃₅ is S. In some embodiments, X₃₆ is S or T. In some embodiments, X₃₆ is S. In some embodiments, X₃₆ is T. In some embodiments, X₃₇ is A or L. In some embodiments, X₃₇ is A. In some embodiments, X₃₇ is L. In some embodiments, X₃₈ is P or V. In some embodiments, X₃₈ is P. In some embodiments, X₃₈ is V. In some embodiments, X₃₉ is D or E. In some embodiments, X₃₉ is D. In some embodiments, X₃₉ is E. In some embodiments, X₄₀ is A or V. In some embodiments, X₄₀ is A. In some embodiments, X₄₀ is V. In some embodiments, X₄₁ is I or L. In some embodiments, X₄₁ is I. In some embodiments, X₄₁ is L. In some embodiments, X₄₂ is S or T. In some embodiments, X₄₂ is S. In some embodiments, X₄₂ is T. In some embodiments, X₄₃ is E or G. In some embodiments, X₄₃ is E. In some embodiments, X₄₃ is G. In some embodiments, X₄₄ is A, N or S. In some embodiments, X₄₄ is A. In some embodiments, X₄₄ is N. In some embodiments, X₄₄ is S. In some embodiments, X₄₅ is L or Y. In some embodiments, X₄₅ is L. In some embodiments, X₄₅ is Y. In some embodiments, X₄₆ is E or G. In some embodiments, X₄₆ is E. In some embodiments, X₄₆ is G. In some embodiments, X₄₇ is K or Q. In some embodiments, X₄₇ is K. In some embodiments, X₄₇ is Q. In some embodiments, X₄₈ is K or R. In some embodiments, X₄₈ is K. In some embodiments, X₄s is R. In some embodiments, X₄₉ is S or T. In some embodiments, X₄₉ is S. In some embodiments, X₄₉ is T. In some embodiments, X₅₀ is A or Q. In some embodiments, X₅₀ is A. In some embodiments, X₅₀ is Q. In some embodiments, X₅₁ is S or T. In some embodiments, X₅₁ is S. In some embodiments, X₅₁ is T. In some embodiments, X₅₂ is I or V. In some embodiments, X₅₂ is I. In some embodiments, X₅₂ is V. In some embodiments, X₅₃ is D or S. In some embodiments, X₅₃ is D. In some embodiments, X₅₃ is S. In some embodiments, X₅₄ is R or S. In some embodiments, X₅₄ is R. In some embodiments, X₅₄ is S. In some embodiments, X₅₅ is E or Q. In some embodiments, X₅₅ is E. In some embodiments, X₅₅ is Q. In some embodiments, X₅₆ is T or V. In some embodiments, X₅₆ is T. In some embodiments, X₅₆ is V. In some embodiments, X₅₇ is L or Q. In some embodiments, X₅₇ is L. In some embodiments, X₅₇ is Q. In some embodiments, X₅s is L or V. In some embodiments, X₅₈ is L. In some embodiments, X₅₈ is V.

In some embodiments, the polypeptide comprises a V_(H) that comprises an HCDR1, an HCDR2 and an HCDR3 that are identical to the HCDR1, HCDR2 and HCDR3, respectively, of SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 41 or SEQ ID NO: 42, SEQ ID NO: 43, SEQ ID NO: 44 or SEQ ID NO: 45 (see Table 1 for SEQ ID NOs: 4-10 and 41-45 and FIGS. 2A, 3A and 4A for corresponding HCDR1, HCDR2 and HCDR3 sequences).

In some embodiments, the polypeptide comprises a V_(L) that comprises a LCDR1, a LCDR2 and a LCDR3 that are identical to the LCDR1, LCDR2 and LCDR3, respectively, of SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 47, SEQ ID NO: 48 or SEQ ID NO: 49 (see Table 1 for SEQ ID NOs: 13-15 and 47-49, and FIGS. 2B, 3B and 4B for corresponding LCDR1, LCDR2 and LCDR3 sequences).

In some embodiments, the polypeptide comprises a paratope that is identical to the paratope of a VHVL combination selected from: SEQ ID NO: 4/SEQ ID NO: 13, SEQ ID NO: 5/SEQ ID NO: 13, SEQ ID NO: 6/SEQ ID NO: 13, SEQ ID NO: 7/SEQ ID NO: 14, SEQ ID NO: 8/SEQ ID NO: 15, SEQ ID NO: 9/SEQ ID NO: 13, SEQ ID NO: 10/SEQ ID NO: 13, SEQ ID NO: 41/SEQ ID NO: 13, SEQ ID NO: 42/SEQ ID NO: 13, SEQ ID NO: 43/SEQ ID NO: 47, SEQ ID NO: 44/SEQ ID NO: 48 or SEQ ID NO: 45/SEQ ID NO: 49. In some embodiments, the polypeptide comprises a paratope that differs from the paratope of a VHVL combination selected from: SEQ ID NO: 4/SEQ ID NO: 13, SEQ ID NO: 5/SEQ ID NO: 13, SEQ ID NO: 6/SEQ ID NO: 13, SEQ ID NO: 7/SEQ ID NO: 14, SEQ ID NO: 8/SEQ ID NO: 15, SEQ ID NO: 9/SEQ ID NO: 13, SEQ ID NO: 10/SEQ ID NO: 13, SEQ ID NO: 41/SEQ ID NO: 13, SEQ ID NO: 42/SEQ ID NO: 13, SEQ ID NO: 43/SEQ ID NO: 47, SEQ ID NO: 44/SEQ ID NO: 48 or SEQ ID NO: 45/SEQ ID NO: 49, by substitution of from 1 to 3 (e.g., 1, 2 or 3) residues. In some embodiments, the polypeptide comprises a paratope that is identical to the paratope of a V_(H)/V_(L) combination selected from: SEQ ID NO: 3/SEQ ID NO: 12.

In some embodiments, the polypeptide disclosed herein comprises a V_(H) that is at least about 70% identical to SEQ ID NO: 3. For example, the V_(H) can be at least about: 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identical to SEQ ID NO: 3. In some embodiments, the V_(H) is at least about 85% or at least about 90% identical to SEQ ID NO: 3. The sequence identified as SEQ ID NO: 3 is shown below, which corresponds to a murine V_(H) domain:

(SEQ ID NO: 3) EVQLEESGTVLARPGASVKMSCKASGYTFTTYRMHWIKQRPGQGLEWIGA IYPGNSDTTYNQKFKDKAKLTAVTSTSSAYMELSSLTNEDSAVYFCTREG IPQLLRTLDYWGQGTSVTVSS

In some embodiments, the polypeptide disclosed herein comprises a V_(H) that is at least about 70% identical to SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 41, SEQ ID NO: 42, SEQ ID NO: 43, SEQ ID NO: 44 or SEQ ID NO: 45, or a combination of the foregoing. For example, the V_(H) can be at least about: 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identical to SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 41 or SEQ ID NO: 42, or a combination of the foregoing. In some embodiments, the V_(H) is at least about 85% or at least about 90% identical to SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 41, SEQ ID NO: 42, SEQ ID NO: 43, SEQ ID NO: 44 or SEQ ID NO: 45, or a combination of the foregoing.

In some embodiments, the polypeptide disclosed herein comprises a V_(L) that is at least about 70% identical to SEQ ID NO: 12. For example, the V_(L) can be at least about: 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identical to SEQ ID NO: 12. In some embodiments, the V_(L) is at least about 85% or at least about 90% identical to SEQ ID NO: 12. The sequence identified as SEQ ID NO: 12 is shown below, which corresponds to a murine V_(L) domain:

(SEQ ID NO: 12) DILMTQSPSSLSASLGERVSLTCRASQEISGYLSWLQEKPDGTIKRLIYA ASTLDSGVPKRFSGSRSGSDYSLTISSLESEDFADYYCLQYVSYPWTFGG GTKLEIK.

In some embodiments, the polypeptide disclosed herein comprises a V_(L) that is at least about 70% identical to SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 47, SEQ ID NO: 48 or SEQ ID NO: 49, or a combination of the foregoing. For example, the V_(L) can be at least about: 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identical to SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 47, SEQ ID NO: 48 or SEQ ID NO: 49, or a combination of the foregoing. In some embodiments, the V_(L) is at least 85% identical to SEQ ID NO: 13, SEQ ID NO: 14 or SEQ ID NO: 15, or a combination of the foregoing. In some embodiments, the V_(L) is at least about 85% or at least about 90% identical to SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 47, SEQ ID NO: 48 or SEQ ID NO: 49, or a combination of the foregoing.

In some embodiments, the polypeptide disclosed herein comprises a V_(H) that comprises at least 1 amino acid substitution relative to SEQ ID NO: 3. For example, the number of amino acid substitutions can be at least about: 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20, or about: 1-20, 1-19, 2-19, 2-18, 2-17, 3-17, 3-16, 4-16, 4-15, 5-15, 5-14, 6-14, 6-13, 7-13, 7-12, 8-12, 8-11 or 9-11. In some embodiments, the V_(H) comprises about 1-10 amino acid substitutions, relative to SEQ ID NO: 3.

In some embodiments, the polypeptide disclosed herein comprises a V_(H) that comprises at least 1 amino acid substitution relative to SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 41, SEQ ID NO: 42, SEQ ID NO: 43, SEQ ID NO: 44 or SEQ ID NO: 45, or a combination of the foregoing. For example, the number of amino acid substitutions can be at least about: 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20, or about: 1-20, 1-19, 2-19, 2-18, 2-17, 3-17, 3-16, 4-16, 4-15, 5-15, 5-14, 6-14, 6-13, 7-13, 7-12, 8-12, 8-11 or 9-11. In some embodiments, the V_(H) comprises about 1-10 amino acid substitutions, relative to SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 41, SEQ ID NO: 42, SEQ ID NO: 43, SEQ ID NO: 44 or SEQ ID NO: 45, or a combination of the foregoing.

In some embodiments, the polypeptide disclosed herein comprises a V_(L) that comprises at least 1 amino acid substitution relative to SEQ ID NO: 12. For example, the number of amino acid substitutions can be at least about: 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20, or about: 1-20, 1-19, 2-19, 2-18, 2-17, 3-17, 3-16, 4-16, 4-15, 5-15, 5-14, 6-14, 6-13, 7-13, 7-12, 8-12, 8-11 or 9-11. In some embodiments, the V_(L) comprises about 1-10 amino acid substitutions, relative to SEQ ID NO: 12.

In some embodiments, the polypeptide disclosed herein comprises a V_(L) that comprises at least 1 amino acid substitution relative to SEQ ID NO: 13, SEQ ID NO: 14 or SEQ ID NO: 15, or a combination of the foregoing. For example, the number of amino acid substitutions can be at least about: 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20, or about: 1-20, 1-19, 2-19, 2-18, 2-17, 3-17, 3-16, 4-16, 4-15, 5-15, 5-14, 6-14, 6-13, 7-13, 7-12, 8-12, 8-11 or 9-11. In some embodiments, the V_(L) comprises about 1-10 amino acid substitutions, relative to SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 47, SEQ ID NO: 48 or SEQ ID NO: 49, or a combination of the foregoing.

In some embodiments, the amino acid substitutions are conservative substitutions. The term “conservative amino acid substitution(s)” or “conservative substitution(s)” refers to an amino acid substitution having a value of 0 or greater in BLOSUM62.

In some embodiments, the amino acid substitutions are highly conservative substitutions. The term “highly conservative amino acid substitution(s)” or “highly conservative substitution(s)” refers to an amino acid substitution having a value of at least 1 (e.g., at least 2) in BLOSUM62.

In some embodiments, the polypeptide disclosed herein comprises a V_(H) that comprises SEQ ID NO: 3. In some embodiments, the polypeptide disclosed herein comprises a V_(H) that comprises SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 41, SEQ ID NO: 42, SEQ ID NO: 43, SEQ ID NO: 44 or SEQ ID NO: 45.

In some embodiments, the polypeptide disclosed herein comprises a V_(L) that comprises SEQ ID NO: 12. In some embodiments, the polypeptide disclosed herein comprises a V_(L) that comprises SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 47, SEQ ID NO: 48 or SEQ ID NO: 49.

In some embodiments, the polypeptide disclosed herein comprises:

-   -   a) a V_(H) comprising SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6,         SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 41 or SEQ ID NO: 42; and     -   b) a V_(L) comprising SEQ ID NO: 13.

In some embodiments, the polypeptide disclosed herein comprises:

-   -   a) a V_(H) comprising SEQ ID NO: 7; and     -   b) a V_(L) comprising SEQ ID NO: 14.

In some embodiments, the polypeptide disclosed herein comprises:

-   -   a) a V_(H) comprising SEQ ID NO: 8; and     -   b) a V_(L) comprising SEQ ID NO: 15.

In some embodiments, the polypeptide disclosed herein comprises a V_(H) and V_(L) that are humanized, contain human framework regions, or a combination thereof.

In some embodiments, the polypeptide disclosed herein comprises:

-   -   a) a V_(H) comprising SEQ ID NO: 43; and     -   b) a V_(L) comprising SEQ ID NO: 47.

In some embodiments, the polypeptide disclosed herein comprises:

-   -   a) a V_(H) comprising SEQ ID NO: 44; and     -   b) a V_(L) comprising SEQ ID NO: 48.

In some embodiments, the polypeptide disclosed herein comprises:

-   -   a) a V_(H) comprising SEQ ID NO: 45; and     -   b) a V_(L) comprising SEQ ID NO: 49.

In some embodiments, the polypeptide disclosed herein is an immunoglobulin molecule, such as an antibody (e.g., a whole antibody, an intact antibody) or an antigen-binding fragment of an antibody.

In some embodiments, the polypeptide disclosed herein is an antibody. As used herein, the term “antibody” refers to an immunoglobulin molecule capable of specific binding to a target, such as a carbohydrate, polynucleotide, lipid, polypeptide, etc., through at least one antigen recognition site, located in the variable region of the immunoglobulin molecule. As used herein, the term “antibody” refers to a full-length antibody comprising two heavy (H) chains and two light (L) chains inter-connected by disulfide bonds or multimers thereof (for example, IgM). Each heavy chain comprises a heavy chain variable region (V_(H)) and a heavy chain constant region (comprising domains CHI, hinge CH2 and CH3). Each light chain comprises a light chain variable region (V_(L)) and a light chain constant region (CL). The V_(H) and the V_(L) regions may be further subdivided into regions of hypervariability, termed complementarity determining regions (CDR), interspersed within framework regions (FR). V_(H) and V_(L) each comprises three CDRs and four FR segments, arranged from the amino-terminus to the carboxy-terminus in the following order: FR1, CDR1, FR2, CDR2, FR3, CDR3, and FR4. The antibody can be of any species, such as a murine antibody, a human antibody or a humanized antibody.

The extent of the framework region and the CDRs of an antibody can be identified using one of several suitable methodologies that are well known in the art, for example, by the Kabat definition, the Chothia definition, the AbM definition, and/or the contact definition. Publicly and/or commercially available tools for identifying framework and/or CDR regions include, IgBlast (accessible at www.ncbi.nlm.nih.gov/igblast/), Scaligner (available from drugdesigntech at www.scaligner.com/), IMGT rules and/or tools (see, for example, www.imgt.org/IMGTScientificChart/Nomenclature/IMGT-FRCDRdefinition.html, also accessible at www.imgt.org/), Chothia Canonical Assignment (accessible at www.bioinforg.uk/abs/chothia.html), Antigen receptor Numbering And Receptor CalssificatiIon (ANARCI, accessible at opig.stats.ox.ac.uk/webapps/newsabdab/sabpred/anarci/), or the Paratome web server (accessible at www.ofranlab.org/paratome/, see Vered Kunik, et al, Nucleic Acids Research, Volume 40, Issue W1, 1 Jul. 2012, Pages W521-W524).

As used herein, a “CDR” encompasses any CDR defined by an art-recognized method for identifying the CDR residues on an antibody. See, e.g., Kabat, E. A., et al., (1991) Sequences of Proteins of Immunological Interest, Fifth Edition, U.S. Department of Health and Human Services, NIH Publication No. 91-3242, Chothia et al., (1989) Nature 342:877; Chothia, C. et al., (1987) J. Mol. Biol. 196:901-917; Al-lazikani et al., (1997) J. Molec. Biol. 273:927-948; and Almagro, J. Mol. Recognit. 17:132-143 (2004). See also hgmp.mrc.ac.uk and bioinf.org.uk/abs. Two antibodies are determined to have the same CDR as one another with respect to a HCDR1, HCDR2, HCDR3, LCDR1, LCDR2 and/or LCDR3, when the identity of that CDR is determined for both antibodies using the same method.

In some embodiments, the polypeptide disclosed herein is an antigen-binding fragment. The term “antigen-binding fragment” refers to a portion of an immunoglobulin molecule (e.g., antibody) that retains the antigen binding properties of the parental full-length antibody. Non-limiting examples of antigen-binding fragments include a V_(H) region, a V_(L) region, an Fab fragment, an F(ab′)2 fragment, an Fd fragment, an Fv fragment, and a domain antibody (dAb) consisting of one V_(H) domain or one V_(L) domain, etc. V_(H) and V_(L) domains may be linked together via a synthetic linker to form various types of single-chain antibody designs in which the V_(H)/V_(L) domains pair intramolecularly, or intermolecularly in those cases when the V_(H) and V_(L) domains are expressed by separate chains, to form a monovalent antigen binding site, such as single chain Fv (scFv) or diabody. In some embodiments, the polypeptide disclosed herein is an antigen binding fragment selected from Fab, F(ab′)2, Fab′, scFv, or Fv. In some embodiments, the polypeptide is a scFv.

In some embodiments, a polypeptide disclosed herein (e.g., an antibody or antigen-binding fragment) is incorporated into a cell-based therapy. In some embodiments, the polypeptide is an engineered T cell receptor. In some embodiments, the polypeptide is a chimeric antigen receptor (CAR) (e.g., expressed on a T (CAR-T) cell, natural killer (CAR-NK) cell, or macrophage (CAR-M) cell). In some embodiments, the CAR comprises a transmembrane domain and an antigen-recognition moiety, wherein the antigen-recognition moiety binds SARS-CoV-2 (e.g., RBD 11).

In some embodiments, the polypeptide is an antibody mimetic. The term “antibody mimetic” refers to polypeptides capable of mimicking an antibody's ability to bind an antigen, but structurally differ from native antibody structures. Non-limiting examples of antibody mimetics include Adnectins, Affibodies, Affilins, Affimers, Affitins, Alphabodies, Anticalins, Avimers, DARPins, Fynomers, Kunitz domain peptides, monobodies, nanobodies, nanoCLAMPs, and Versabodies.

In some embodiments, the polypeptide of the invention competes with a reference antibody for binding to the wildtype SARS-CoV-1-Spike, a SARS-CoV-1-Spike variant, or a combination thereof, wherein the reference antibody specifically binds the wildtype SARS-CoV-1-Spike. The term “specifically binding” or “specifically binds” refers to preferential interaction, i.e., significantly higher binding affinity, between an antibody, or an antigen-binding fragment thereof, and its epitope relative to other antigens or amino acid sequences. In some embodiments, the reference antibody comprises a V_(H) sequence of SEQ ID NO: 3 and a V_(L) sequence of SEQ ID NO: 12. In some embodiments, the reference antibody comprises HCDR1, HCDR2 and HCDR3 sequences of SEQ ID NO: 17, SEQ ID NO: 21 and SEQ ID NO: 24, respectively. In some embodiments, the reference antibody comprises LCDR1, LCDR2 and LCDR3 sequences of SEQ ID NO: 32, SEQ ID NO: 33 and SEQ ID NO: 35, respectively. In some embodiments, the reference antibody comprises HCDR1, HCDR2 and HCDR3 sequences of SEQ ID NO: 17, SEQ ID NO: 21 and SEQ ID NO: 24, respectively; and LCDR1, LCDR2 and LCDR3 sequences of SEQ ID NO: 32, SEQ ID NO: 33 and SEQ ID NO: 35, respectively.

In some embodiments, the polypeptide further comprises:

-   -   a) an antibody heavy chain constant region sequence;     -   b) an antibody light chain constant region sequence; or     -   c) both an antibody heavy chain constant region sequence and an         antibody light chain constant region sequence.

In some embodiments, the antibody heavy chain constant region is selected from the group consisting of an IgA constant region, an IgD constant region, an IgE constant region, an IgG constant region and an IgM constant region. In some embodiments, the IgG constant region is an IgG1 constant region, an IgG2 constant region, an IgG3 constant region or an IgG4 constant region. In some embodiments, the IgG2 constant region is an IgG2a, an IgG2b constant region or an IgG2c constant region. In some embodiments, the IgA constant region is an IgA1 constant region or an IgA2 constant region. In some embodiments, the antibody heavy chain constant region is an IgG1 constant region (e.g., IGHV1-5).

In some embodiments, the antibody light chain constant region is selected from the group consisting of a x constant region and a X constant region. In some embodiments, the antibody light chain constant region is a x constant region.

In some embodiments, the antibody heavy chain constant region is an IgG1 constant region, and the antibody light chain constant region is a x constant region.

In some embodiments, the antibody heavy chain constant region sequence is at least about 60% identical to SEQ ID NO: 38. For example, the antibody heavy chain constant region sequence can be at least about: 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identical to SEQ ID NO: 38. In some embodiments, the antibody heavy chain constant region sequence is at least about 70% or at least about 80% identical to SEQ ID NO: 38. The sequence identified as SEQ ID NO: 38 is shown below:

(SEQ ID NO: 38) ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGV HTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEP KSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVS HEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGK EYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTC LVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRW QQGNVFSCSVMHEALHNHYTQKSLSLSPGK.

In some embodiments, the antibody light chain constant region sequence is at least about 60% identical to SEQ ID NO: 39 or SEQ ID NO: 40. For example, the antibody light chain constant region sequence can be at least about: 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99% identical to SEQ ID NO: 39 or SEQ ID NO: 40. In some embodiments, the antibody light chain constant region sequence is at least about 70% or at least about 80% identical to SEQ ID NO: 39 or SEQ ID NO: 40. The sequences identified as SEQ ID NO: 39 and SEQ ID NO: 40 are shown below:

(SEQ ID NO: 39) RTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSG NSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEVTHQGLSSPVTK SFNRGEC. (SEQ ID NO: 40) GQPKANPTVTLFPPSSEELQANKATLVCLISDFYPGAVTVAWKADGSPVK AGVETTKPSKQSNNKYAASSYLSLTPEQWKSHRSYSCQVTHEGSTVEKTV APTECS.

In some embodiments, the antibody heavy chain constant region sequence comprises at least 1 amino acid substitution relative to SEQ ID NO: 38. For example, the number of amino acid substitutions can be at least about: 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20, or about: 1-20, 1-19, 2-19, 2-18, 2-17, 3-17, 3-16, 4-16, 4-15, 5-15, 5-14, 6-14, 6-13, 7-13, 7-12, 8-12, 8-11 or 9-11. In some embodiments, the antibody heavy chain constant region sequence comprises about 1-10 amino acid substitutions, relative to SEQ ID NO: 38.

In some embodiments, the antibody light chain constant region sequence comprises at least 1 amino acid substitution relative to SEQ ID NO: 39 or SEQ ID NO: 40. For example, the number of amino acid substitutions can be at least about: 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20, or about: 1-20, 1-19, 2-19, 2-18, 2-17, 3-17, 3-16, 4-16, 4-15, 5-15, 5-14, 6-14, 6-13, 7-13, 7-12, 8-12, 8-11 or 9-11. In some embodiments, the antibody light chain constant region sequence comprises about 1-10 amino acid substitutions, relative to SEQ ID NO: 39 or SEQ ID NO: 40.

In some embodiments, the amino acid substitutions are conservative substitutions. In some embodiments, the amino acid substitutions are highly conservative substitutions.

In some embodiments, the polypeptide of the invention is an isolated polypeptide. In some embodiments, the isolated polypeptide is recombinantly produced. In some embodiments, the isolated polypeptide is synthetically produced.

In some embodiments, the polypeptide is conjugated to a heterologous moiety. The term “conjugated” refers to attached, via a covalent or noncovalent interaction. Conjugation can employ any of suitable linking agents. Non-limiting examples include peptide linkers, compound linkers, and chemical cross-linking agents.

In some embodiments, the heterologous moiety is a therapeutic agent, a diagnostic agent or a combination thereof. In some embodiments, the heterologous moiety is polyethylene glycol (PEG), hexadecanoic acid, hydrogels, nanoparticles, multimerization domains and carrier peptides.

In some embodiments, the nanoparticle is a lipid nanoparticle. In some embodiments, the nanoparticle is a polymer nanoparticle. In some embodiments, the polymer is an amphiphilic polymer. In other embodiments, the polymer is a hydrophobic or hydrophilic polymer. Non-limiting examples of polymers include poly(lactic acid)-poly(ethylene glycol), poly(lactic-co-glycolic acid)-poly(ethylene glycol), poly(lactic-co-glycolic) acid (PLGA), poly(lactic-co-glycolic acid)-d-α-tocopheryl polyethylene glycol succinate, poly(lactic-co-glycolic acid)-ethylene oxide fumarate, poly(glycolic acid)-poly(ethylene glycol), polycaprolactone-poly(ethylene glycol), or any salts thereof. In some embodiments, the polymer nanoparticle comprises poly(lactic-co-glycolic) acid (PLGA).

In some embodiments, the carrier polypeptide is albumin or an Fc polypeptide.

In some embodiments, the polypeptide:

-   -   a) is capable of binding to an epitope in the receptor-binding         domain of SARS-CoV-2-Spike;     -   b) binds SARS-CoV-2 with an affinity of 10 μM or less;     -   c) reduces binding of SARS-CoV-2 to angiotensin-converting         enzyme 2 (ACE2); or d) reduces infectivity of SARS-CoV-2 in         human cells, or a combination of any of the foregoing.

In some embodiments, the polypeptide is capable of binding to an epitope in the receptor-binding domain of SARS-CoV-2-Spike.

In some embodiments, the polypeptide binds SARS-CoV-2-Spike with a binding constant (KD) of about 10 μM or less. As used herein the term “KD,” also referred to as “binding constant,” “equilibrium dissociation constant” or “affinity constant,” is a measure of the extent of a reversible association between two molecular species (e.g., antibody and target protein) and includes both the actual binding affinity as well as the apparent binding affinity. Binding affinity can be determined using methods known in the art including, for example, by measurement of surface plasmon resonance, e.g., using a Biolayer interferometry (Octet, ForteBio) or a surface plasmon resonance (Biacore) system and assay. A reference that compares various surface technologies for measuring binding affinity and kinetics is Yang, D., Singh, A., Wu, H., & Kroe-Barrett, R., Comparison of biosensor platforms in the evaluation of high affinity antibody-antigen binding kinetics, Analytical Biochemistry 508: 78-96 (2016), the contents of which are incorporated by reference herein in their entirety.

In some embodiments, the polypeptide binds SARS-CoV-2-Spike with a KD of about: 5 μM, 2 μM, 1 μM, 500 nM, 200 nM, 100 nM, 50 nM, 20 nM, 10 nM, 5 nM, 2 nM, 1 nM, 0.5 nM, 0.2 nM or 0.1 nM or less. In some embodiments, the polypeptide binds SARS-CoV-2 with a KD of 100 nM or less.

In some embodiments, the polypeptide binds SARS-CoV-2-Spike with a KD of about: 10⁻¹⁰-10⁻⁵ M, 10⁻¹⁰-5×10⁻⁶ M, 2×10⁻¹⁰-5×10⁻⁶ M, 2×10⁻¹⁰-2×10⁻⁶ M, 5×10⁻¹⁰-2×10⁻⁶ M, 5×10⁻¹⁰-10⁻⁷ M, 10⁻⁹-10⁻⁷ M, 10⁻⁹-5×10⁻⁸ M, 2 ×10⁻⁹-5×10⁻⁸ M, 2 ×10⁻⁹-2 ×10⁻⁸ M, 5×10⁻⁹-2 ×10⁻⁸ M or 5×10⁻⁹-10⁻⁸ M.

In some embodiments, the polypeptide (e.g., full-length IgG1 antibody) binds SARS-CoV-2-Spike or a fragment thereof (e.g., the RBD5 epitope) or a variant thereof with a KD of about 10⁻⁶ M or less, e.g., about: 500 nM, 200 nM, 100 nM, 50 nM, 20 nM, 10 nM, 5 nM, 2 nM, 1 nM, 0.5 nM, 0.2 nM or 0.1 nM or less; or about: 10⁻¹⁰-10⁻⁶ M, 10⁻¹⁰-5×10⁻⁷ M, 2 ×10⁻¹⁰-5×10⁻⁷ M, 2 ×10⁻¹⁰-2 ×10⁻⁷ M, 5×10⁻¹⁰-2 ×10⁻⁷ M, 5×10⁻¹⁰-10⁻⁷ M, 10⁻⁹-10⁻⁷ M, 10⁻⁹-5×10⁻⁸ M, 2 ×10⁻⁹-5×10⁻⁸ M, 2 ×10⁻⁹-2 ×10⁻⁸ M, 5×10⁻⁹-2 ×10⁻⁸ M or 5×10⁻⁹-10⁻⁸ M.

In some embodiments, the polypeptide binds SARS-CoV-1-Spike with a KD of about 10 μM or less. In some embodiments, the KD is about: 5 μM, 2 μM, 1 μM, 500 nM, 200 nM, 100 nM, 50 nM, 20 nM, 10 nM, 5 nM, 2 nM, 1 nM, 0.5 nM, 0.2 nM or 0.1 nM or less. In some embodiments, the polypeptide binds SARS-CoV-1-Spike with a KD of about: 10⁻¹⁰10⁻⁵ M, 10⁻¹⁰-5×10⁻⁶ M, 2 ×10⁻¹⁰-5×10⁻⁶ M, 2 ×10⁻¹⁰-2 ×10⁻⁶ M, 5×10⁻¹⁰-2 ×10⁻⁶ M, 5×10⁻¹⁰-10⁻⁷ M, 10⁻-10⁻⁷ M, 10⁻⁹-5×10⁻⁸ M, 2 ×10⁻⁹-5×10⁻⁸ M, 2 ×10⁻⁹-2 ×10⁻⁸ M, 5×10⁻⁹-2 ×10⁻⁸ M or 5×10⁻⁹-10⁻⁸ M.

In some embodiments, the polypeptide (e.g., full-length IgG1 antibody) binds SARS-CoV-2-Spike or a fragment thereof (e.g., the RBD5 epitope) or a variant thereof with an association constant of about 10⁶/Ms or less, e.g., about: 5×10⁵/Ms, 2×10⁵/Ms, 10⁵//Ms, 5×10⁴/Ms, 2×10⁴/Ms, 10⁴/Ms or less; or about: 10⁴-10⁶/Ms, 10⁴-5×10⁵/Ms, 2×10⁴-5×10⁵/Ms, 2×10⁴-2×10⁵/Ms, 5×10⁴-2×10⁵/Ms or 5×10⁴-10⁵/Ms.

In some embodiments, the polypeptide (e.g., full-length IgG1 antibody) binds SARS-CoV-2-Spike or a fragment thereof (e.g., the RBD5 epitope) or a variant thereof with a dissociation constant of about 10⁻²/s or less, e.g., about: 8×10⁻³/s, 6×10⁻³/s, 4×10⁻³/s, 2 ×10⁻³/s, 10 ⁻³/s, 8×10⁻⁴/s, 6×10⁻⁴/s, 4×10⁻⁴/s, 2×10⁻⁴/s 10⁻⁴/s, 8 ×10⁻⁵/s, 6×10⁻⁵/s, 4×10⁻⁵/s, 2×10⁻⁵/s 10⁻⁵/s, 8×10 ⁻⁶/s, 6×10⁻⁶/s, 4×10⁻⁶/s, 2 ×10⁻⁶/S or 10⁻⁶/S, or less; or about: 10⁻⁶-10⁻²/S, 2×10⁻⁶-10⁻²/s, 2 ×10⁻⁶-5×10 ⁻³/s, 5×10⁻⁶-5×10⁻³/s, 5×10⁻⁶-2 ×10⁻³/s, 10⁻⁵-2 ×10⁻³/s, 10⁻⁵-10⁻³/s, 2 ×10⁻⁵-10⁻³/s, 2 ×10⁻⁵-5×10⁻⁴/s, 5×10⁻⁵-5×10⁻⁴/s, 5×10⁻⁵-2 ×10⁻⁴/s or 10⁻⁴-2 ×10⁻⁴/s.

In some embodiments, the polypeptide (e.g., full-length IgG1 antibody) binds SARS-CoV-2-Spike or a fragment thereof (e.g., the RBD5 epitope) or a variant thereof with a R_(max) of about 0.05 or more, e.g., about: 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75 or 0.8 or more; or about: 0.1-0.8, 0.15-0.8, 0.15-0.75, 0.2-0.75, 0.2-0.7, 0.25-0.7, 0.25-0.65, 0.3-0.65, 0.3-0.6, 0.35-0.6, 0.35-0.55, 0.4-0.55 or 0.4-0.5.

In some embodiments, the polypeptide reduces binding of SARS-CoV-2-Spike to an entry receptor (e.g., ACE2).

In some embodiments, the entry receptor is ACE2. In some embodiments, the ACE2 is a mammalian ACE2. In some embodiments, the ACE2 is a primate ACE2. In some embodiments, the primate ACE2 is human ACE2 (GeneTD 59272; exemplary protein sequence NP_001358344.1). In some embodiments, the primate ACE2 is a non-human primate ACE2 selected from the group consisting of chimpanzee ACE2 (e.g., AOA2J8KU96, XP_016798468.1, XP_016798469.1, PNI38578.1), macaque ACE2 (e.g., B6DUF2, NP_001129168.1, XP_024647450.1), cynomolgus ACE2 (e.g., A0A2K5X₂₈₃, XP_005593094.1) and combinations thereof.

In some embodiments, the polypeptide reduces binding of SARS-CoV-2-Spike to its cellular target receptor (e.g., ACE2) by at least about 10%. For example, by at least about: 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%. In some embodiments, the polypeptide reduces binding of SARS-CoV-2-Spike to ACE2 by at least about 30%.

In some embodiments, the level of binding between SARS-CoV-2-Spike and its cellular target receptor (e.g., ACE2) in the presence of the polypeptide is less than about 90% relative to the level of binding in the absence of the polypeptide, for example, less than about: 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2% or 1%.

In some embodiments, the level of binding between SARS-CoV-2-Spike and its cellular target receptor (e.g., ACE2) in the presence of the polypeptide is about 1-90% relative to the level of binding in the absence of the polypeptide, for example, about: ²-90%, 2-85%, 3-85%, 3-80%, 4-80%, 4-75%, 5-75%, 5-70%, 6-70%, 6-65%, 7-65%, 7-60%, 8-60%, 8-55%, 9-55%, 9-50%, 10-50%, 10-45%, 15-45%, 15-40%, 20-40%, 20-35%, 25-35% or 25-30%, relative to the level of binding in the absence of the polypeptide.

In some embodiments, the polypeptide reduces binding of SARS-CoV-1-Spike to its cellular target receptor by at least about 10%. For example, by at least about: 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%.

In some embodiments, the polypeptide (e.g., full-length IgG1 antibody) neutralizes the SARS-CoV-2 infectivity of human host cells with an IC₅₀ of about 25,000 ng/mL or less, e.g., about: 20,000 ng/mL, 15,000 ng/mL, 10,000 ng/mL, 5,000 ng/mL, 2,500 ng/mL, 1,000 ng/mL, 750 ng/mL, 500 ng/mL, 250 ng/mL, 100 ng/mL, 75 ng/mL, 50 ng/mL, 25 ng/mL or 10 ng/mL or less; e.g., about: 10-25,000 ng/mL, 10-20,000 ng/mL, 25-20,000 ng/mL, 25-15,000 ng/mL, 50-15,000 ng/mL, 50-10,000 ng/mL, 75-10,000 ng/mL, 75-5,000 ng/mL, 100-5,000 ng/mL, 100-2,500 ng/mL, 250-2,500 ng/mL, 250-1,000 ng/mL, 500-1,000 ng/mL or 500-750 ng/mL.

In some embodiments, the polypeptide (e.g., full-length IgG1 antibody) neutralizes the SARS-CoV-2 infectivity of human host cells with an ICso of about 50,000 ng/mL or less, e.g., about: 25,000 ng/mL, 15,000 ng/mL, 10,000 ng/mL, 5,000 ng/mL, 2,500 ng/mL, 1,000 ng/mL, 750 ng/mL, 500 ng/mL, 250 ng/mL, 100 ng/mL, 75 ng/mL, 50 ng/mL, 25 ng/mL or 10 ng/mL or less; e.g., about: 10-50,000 ng/mL, 10-25,000 ng/mL, 25-25,000 ng/mL, 25-15,000 ng/mL, 50-15,000 ng/mL, 50-10,000 ng/mL, 75-10,000 ng/mL, 75-5,000 ng/mL, 100-5,000 ng/mL, 100-2,500 ng/mL, 250-2,500 ng/mL, 250-1,000 ng/mL, 500-1,000 ng/mL or 500-750 ng/mL.

In some embodiments, the polypeptide reduces binding of SARS-CoV-2 to a host protease (e.g., the Type II transmembrane serine protease (TMPRSS2)). Without being bound to theory, the main host protease that mediates SARS-CoV-2-Spike activation on primary target cells and initial viral entry is TMPRSS2.

In some embodiments, the host protease is TMPRSS2. In some embodiments, the TMPRSS2 is a mammalian TMPRSS2. In some embodiments, the TMPRSS2 is a primate TMPRSS2, e.g., human TMPRSS2 or a non-human primate TMPRSS2 (e.g., chimpanzee TMPRSS2, macaque TMPRSS2 or cynomolgus TMPRSS2).

In some embodiments, the polypeptide reduces binding of SARS-CoV-2 to the host protease (e.g., TMPRSS2) by at least about 10%, e.g., by at least about: 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%.

In some embodiments, the level of binding between SARS-CoV-2 and the host protease (e.g., TMPRSS2) in the presence of the polypeptide is less than about 90% relative to the level of binding in the absence of the polypeptide, for example, less than about: 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 9%, 8%, 7%, 6%, 500⁴⁰, 3%, 2% or 1%.

In some embodiments, the level of binding between SARS-CoV-2 and the host protease (e.g., TMPRSS2) in the presence of the polypeptide is about 1-90% relative to the level of binding in the absence of the polypeptide, for example, about: 2-90%, 2-85%, 3-85%, 3-80%, 4-80%, 4-75%, 5-75%, 5-70%, 6-70%, 6-65%, 7-65%, 7-60%, 8-60%, 8-55%, 9-55%, 9-50%, 10-50%, 10-45%, 15-45%, 15-40%, 20-40%, 20-35%, 25-35% or 25-30%, relative to the level of binding in the absence of the polypeptide.

In some embodiments, the polypeptide reduces entry of SARS-CoV-2 into host cells (e.g., human host cells). In some embodiments, the polypeptide reduces entry of SARS-CoV-2 into host cells by at least about 10%, e.g., by at least about: 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%.

In some embodiments, the polypeptide reduces infectivity of SARS-CoV-2 in host cells (e.g., human host cells). In some embodiments, the polypeptide reduces infectivity of SARS-CoV-2 in host cells (e.g., human host cells) by at least about 10%, e.g., by at least about: 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%. In some embodiments, the polypeptide reduces infectivity of SARS-CoV-2 in human cells by at least about 30%.

In some embodiments, the polypeptide reduces re-infection of SARS-CoV-2 in host cells (e.g., human host cells). In some embodiments, the polypeptide reduces re-infection of SARS-CoV-2 in host cells (e.g., human host cells) by at least about 10%, e.g., by at least about: 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%. In some embodiments, the polypeptide reduces re-infection of SARS-CoV-2 in human cells by at least about 30%.

Infectivity or re-infection can be measured using techniques such as a pseudovirus neutralization assay or a live virus neutralization assay (see, e.g., Pinto et al., Cross-neutralization of SARS-CoV-2 by a human monoclonal SARS-CoV antibody, Nature 583: 290-95 (2020), the contents of which are incorporated herein by reference). A kit, for example, the GenScript cPass™ SARS-CoV-2 neutralization antibody detection kit, can be used according to manufacturer's protocol.

In some embodiments, the host cells are selected from the group consisting of lung type II pneumocytes, ileal absorptive enterocytes, nasal goblet secretory cells, and combinations thereof.

Fusion Proteins

In another aspect, the invention provides a fusion protein comprising one or more of the polypeptides described herein.

The term “fusion protein” refers to a synthetic, semi-synthetic or recombinant single protein molecule. A fusion protein can comprise all or a portion of two or more different proteins and/or polypeptides that are attached by covalent bonds (e.g., peptide bonds).

Fusion proteins of the invention can be produced recombinantly or synthetically, using routine methods and reagents that are well known in the art. For example, a fusion protein of the invention can be produced recombinantly in a suitable host cell (e.g., bacteria) according to methods known in the art. See, e.g., Current Protocols in Molecular Biology, Second Edition, Ausubel et al. eds., John Wiley & Sons, 1992; and Molecular Cloning: a Laboratory Manual, 2nd edition, Sambrook et al., 1989, Cold Spring Harbor Laboratory Press. For example, a nucleic acid molecule comprising a nucleotide sequence encoding a fusion protein described herein can be introduced and expressed in suitable host cell (e.g., E. coli), and the expressed fusion protein can be isolated/purified from the host cell (e.g., in inclusion bodies) using routine methods and readily available reagents. For example, DNA fragments coding for different protein sequences (e.g., a light-responsive domain, a heterologous peptide component) can be ligated together in-frame in accordance with conventional techniques. In another embodiment, the fusion gene can be synthesized by conventional techniques including automated DNA synthesizers. Alternatively, PCR amplification of nucleic acid fragments can be carried out using anchor primers that give rise to complementary overhangs between two consecutive nucleic acid fragments that can subsequently be annealed and re-amplified to generate a chimeric nucleic acid sequence (see Ausubel et al., Current Protocols in Molecular Biology, 1992).

Nucleic Acids, Expression Vectors, Expression Host Cells

In another aspect, the invention provides one or more polynucleotides encoding any one of the polypeptides or fusion proteins described herein. In some embodiments, the polypeptide or fusion protein of the invention is encoded by a single polynucleotide. In some embodiments, the polypeptide or fusion protein of the invention is encoded by multiple polynucleotides.

In some embodiments, the polynucleotide comprises a nucleotide sequence that is codon-optimized for a chosen host cell.

In another aspect, the invention provides an expression vector comprising any one or more of the polynucleotides described herein.

The term “expression vector” refers to a replicable nucleic acid from which one or more proteins can be expressed when the expression vector is transformed into a suitable expression host cell.

In some embodiments, the expression vector further comprises an expression control polynucleotide sequence operably linked to the polynucleotide, a polynucleotide sequence encoding a selectable marker, or both. In some embodiments, the expression control polynucleotide sequence comprises a promoter sequence, an enhancer sequence, or both. In some embodiments, the expression control polynucleotide sequence comprises an inducible promoter sequence. The term “promoter” refers to a region of DNA to which RNA polymerase binds and initiates the transcription of a gene. The term “operably linked” means that the nucleic acid is positioned in the recombinant polynucleotide, e.g., vector, in such a way that enables expression of the nucleic acid under control of the element (e.g., promoter) to which it is linked. The term “selectable marker element” is an element that confers a trait suitable for artificial selection. Selectable marker elements can be negative or positive selection markers.

In another aspect, the invention provides an expression host cell comprising any one or more of the polynucleotides or expression vectors described herein.

The term “expression host cell” refers to a cell useful for receiving, maintaining, reproducing and/or amplifying a vector.

Non-limiting examples of expression host cells include mammalian cells such as hybridoma cells, Chinese hamster ovary (CHO) cells, COS cells, human embryonic kidney (HEK), yeast cells such as Pichia pastoris cells, or bacterial cells such as DH5a, etc.

Compositions

In another aspect, the invention provides a composition comprising any one of the polypeptides or fusion proteins described herein. In some embodiments, the composition is a pharmaceutical composition.

In some embodiments, the composition (e.g., pharmaceutical composition) further comprises pharmaceutically acceptable carriers, excipients, stabilizers, diluents or tonifiers (Remington's Pharmaceutical Sciences 16th edition, Osol, A. Ed. (1980)). Suitable pharmaceutically acceptable carriers, excipients, or stabilizers are nontoxic to recipients at the dosages and concentrations employed. Non-limiting examples of pharmaceutically acceptable carriers, excipients, stabilizers, diluents or tonifiers include buffers (e.g., phosphate, citrate, histidine), antioxidants (e.g., ascorbic acid or methionine), preservatives, proteins (e.g., serum albumin, gelatin or immunoglobulins); hydrophilic polymers, amino acids, carbohydrates (e.g., monosaccharides, disaccharides, glucose, mannose or dextrins); chelating agents (e.g., EDTA), sugars (e.g., sucrose, mannitol, trehalose or sorbitol), salt-forming counter-ions (e.g., sodium), metal complexes (e.g., Zn-protein complexes); non-ionic surfactants (e.g., Tween), PLURONICS™ and polyethylene glycol (PEG).

In some embodiments, the composition (e.g., pharmaceutical composition) of the invention is formulated for a suitable administration schedule and route. Non-limiting examples of administration routes include oral, rectal, mucosal, intravenous, intramuscular, subcutaneous and topical, etc. In some embodiments, the composition (e.g., pharmaceutical composition) of the invention is stored in the form of an aqueous solution or a dried formulation (e.g., lyophilized).

In some embodiments, the composition is formulated to be administered by infusion (e.g., intravenous infusion).

In some embodiments, the composition is formulated to be administered with a second therapeutic agent as a combination therapy.

Methods of Use

In another aspect, the invention provides a method of reducing the likelihood of a SARS-CoV-2 infection in a subject, comprising administering to the subject an effective amount of a pharmaceutical composition comprising a pharmaceutically acceptable carrier and, wherein as an active ingredient, any one of the polypeptides or fusion proteins described herein.

In some embodiments, the likelihood of SARS-CoV-2 infection in the subject is reduced by at least about 10%, e.g., by at least about: 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%.

In some embodiments, the likelihood of SARS-CoV-2 infection in the subject in the presence of the polypeptide is about 1-90% relative to the likelihood in the absence of the polypeptide, for example, about: 2-90%, 2-85%, 3-85%, 3-80%, 4-80%, 4-75%, 5-75%, 5-70%, 6-70%, 6-65%, 7-65%, 7-60%, 8-60%, 8-55%, 9-55%, 9-50%, 10-50%, 10-45%, 15-45%, 15-40%, 20-40%, 20-35%, 25-35% or 25-30%.

The term “subject” or “patient” refers to an animal (e.g., a mammal). A subject to be treated according to the methods described herein may be one who has been diagnosed with a particular condition (e.g., COVID-19), or one at risk of developing such conditions. Diagnosis may be performed by any method or technique known in the art. One skilled in the art will understand that a subject to be treated according to the present disclosure may have been subjected to standard tests or may have been identified, without examination, as one at risk due to the presence of one or more risk factors associated with the disease or condition.

In some embodiments, the subject has COVID-19. In some embodiments, the subject has been diagnosed with COVID-19. In other embodiments, the subject is at risk of developing COVID-19.

In some embodiments, the subject is a mammal. In some embodiments, the subject is a mammal selected from the group consisting of a dog, a cat, a mouse, a rat, a hamster, a guinea pig, a horse, a pig, a sheep, a cow, a chimpanzee, a macaque, a cynomolgus, and a human. In some embodiments, the subject is a primate. In some embodiments, the subject is a human.

In some embodiments, the subject has a heart disease. In some embodiments, the subject has a heart disease selected from the group consisting of a congenital heart disease, a coronary artery disease, a hypertensive heart disease, an inflammatory heart disease, a pulmonary heart disease, a rheumatic heart disease, a valvular heart disease, a cardiomyopathy, heart failure, and combinations thereof. In some embodiments, the subject has a congestive heart failure. In some embodiments, the subject has an inflammatory heart disease selected from the group consisting of endocarditis, cardiomegaly, myocarditis, and combinations thereof.

In some embodiments, the subject has diabetes.

In some embodiments, the subject has a lung disease. Non-limiting examples of lung diseases include acute respiratory distress syndromes, asthma, bronchitis, COPD, emphysema, lung tumors, pleural cavity diseases (e.g., pleural mesothelioma or tension pneumothorax), pulmonary vascular diseases (e.g., embolisms, edema, arterial hypertension or hemorrhage), respiratory tract infections (e.g., pneumonia or other upper or lower respiratory tract infections).

In some embodiments, the subject is a tobacco smoker.

In some embodiments, the subject is immune-compromised (e.g., has an underlying disorder or is on immunosuppressive therapy).

In some embodiments, the subject is 40 years or older, e.g., at least: 45, 50, 55, 60, 65, 70, 75, 80, 85, 90 years old.

“A therapeutically effective amount,” “an effective amount” or “an effective dosage” is an amount effective, at dosages and for periods of time necessary, to achieve a desired therapeutic result (e.g., treatment, healing, inhibition or amelioration of physiological response or condition, etc.). The full therapeutic effect does not necessarily occur by administration of one dose, and may occur only after administration of a series of doses. Thus, a therapeutically effective amount may be administered in one or more administrations. A therapeutically effective amount may vary according to factors such as disease state, age, sex, and weight of a mammal, mode of administration and the ability of a therapeutic, or combination of therapeutics, to elicit a desired response in an individual.

An effective amount of an agent to be administered can be determined by a clinician of ordinary skill using the guidance provided herein and other methods known in the art. Relevant factors include the given agent, the pharmaceutical formulation, the route of administration, the type of disease or disorder, the identity of the subject (e.g., age, sex, weight) or host being treated, and the like. For example, suitable dosages can be from about 0.001 mg/kg to about 100 mg/kg, from about 0.01 mg/kg to about 100 mg/kg, from about 0.01 mg/kg to about 10 mg/kg, from about 0.01 mg/kg to about 1 mg/kg body weight per treatment. Determining the dosage for a particular agent, subject and disease is well within the abilities of one of skill in the art. Preferably, the dosage does not cause or produces minimal adverse side effects.

Desired response or desired results include effects at the cellular level, tissue level, or clinical results. As such, “a therapeutically effective amount” or synonym thereto depends upon the context in which it is being applied. For example, in some embodiments it is an amount of the composition sufficient to achieve a treatment response as compared to the response obtained without administration of the composition. In other embodiments, it is an amount that results in a beneficial or desired result in a subject as compared to a control. As defined herein, a therapeutically effective amount of a composition of the present disclosure may be readily determined by one of ordinary skill by routine methods known in the art. Dosage regimen and route of administration may be adjusted to provide the optimum therapeutic response.

In some embodiments, the method is used for prophylactic therapy. In some embodiments, the effective dosage is sufficient to prevent the subject of being infected by SARS-CoV-2.

In some embodiments, the method is used for treating SARS-CoV-2 infection. The term “treating” or “treatment” refers to the medical management of a subject with the intent to improve, ameliorate, stabilize (i.e., not worsen), prevent or cure a disease, pathological condition, or disorder-such as the particular indications exemplified herein. This term includes active treatment (treatment directed to improve the disease, pathological condition, or disorder), causal treatment (treatment directed to the cause of the associated disease, pathological condition, or disorder), palliative treatment (treatment designed for the relief of symptoms), preventative treatment (treatment directed to minimizing or partially or completely inhibiting the development of the associated disease, pathological condition, or disorder); and supportive treatment (treatment employed to supplement another therapy). Treatment also includes diminishment of the extent of the disease or condition; preventing spread of the disease or condition; delay or slowing the progress of the disease or condition; amelioration or palliation of the disease or condition; and remission (whether partial or total), whether detectable or undetectable. “Ameliorating” or “palliating” a disease or condition means that the extent and/or undesirable clinical manifestations of the disease, disorder, or condition are lessened and/or time course of the progression is slowed or lengthened, as compared to the extent or time course in the absence of treatment. “Treatment” can also mean prolonging survival as compared to expected survival if not receiving treatment. Those in need of treatment include those already with the condition or disorder, as well as those prone to have the condition or disorder or those in which the condition or disorder is to be prevented.

In some embodiments, the effective dosage is sufficient to reduce viral load in the subject. In some embodiments, the reduction in viral load is by at least about 10%, e.g., by at least about: 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%. In some embodiments, the reduction in viral load is about 10-99%, e.g., about: 10-98%, 15-98%, 15-97%, 20-97%, 20-96%, 25-96%, 25-95%, 30-95%, 30-94%, 35-94%, 35-93%, 40-93%, 40-92%, 45-92%, 45-91%, 50-91%, 50-90%, 55-90%, 55-85%, 60-85%, 60-80%, 65-80%, 65-75%, or 70-75%.

In some embodiments, the effective dosage is sufficient to inhibit binding of the virus to its target proteins, target cells, or both. In some embodiments, the reduction in binding is by at least about 10%, e.g., by at least about: 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%. In some embodiments, the reduction in binding is about 10⁻⁹⁹%, e.g., about: 10⁻⁹⁸%, 15⁻⁹⁸%, 15-97%, 20-97%, 20-96%, 25-96%, 25-95%, 30-95%, 30-94%, 35-94%, 35-93%, 40-93%, 40-92%, 45-92%, 45-91%, 50-91%, 50-90%, 55-90%, 55-85%, 60-85%, 60-80%, 65-80%, 65-75%, or 70-75%.

In some embodiments, the effective dosage is sufficient to inhibit virus mediated fusion with a target cell. In some embodiments, the reduction in fusion is by at least about 10%, e.g., by at least about: 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%. In some embodiments, the reduction in fusion is about 10⁻⁹⁹%, e.g., about: 10⁻⁹⁸%, 15⁻⁹⁸%, 15⁻⁹⁷%, 20-97%, 20-96%, 25-96%, 25-95%, 30-95%, 30-94%, 35-94%, 35-93%, 40-93%, 40-92%, 45-92%, 45-91%, 50-91%, 50-90%, 55-90%, 55-85%, 60-85%, 60-80%, 65-80%, 65-75%, or 70-75%.

In some embodiments, the effective dosage is sufficient to interfere with conformational changes in the viral envelope proteins necessary for cell infectivity.

A therapeutic agent described herein can be administered via a variety of routes of administration, including, for example, oral, dietary, topical, transdermal, rectal, parenteral (e.g., intra-arterial, intravenous, intramuscular, subcutaneous injection, intradermal injection), intravenous infusion and inhalation (e.g., intrabronchial, intranasal or oral inhalation, intranasal drops) routes of administration, depending on the compound and the particular disease to be treated. Administration can be local or systemic as indicated. The preferred mode of administration can vary depending on the particular compound chosen.

In some embodiments, a polypeptide, composition, or pharmaceutical composition disclosed herein is administered to a subject in combination with one or more additional therapeutic agents (e.g., concurrently or sequentially with one or more additional therapeutic agents). In some embodiments, a subject has been previously treated with one or more therapeutic agents prior to being administered a polypeptide, composition, or pharmaceutical composition disclosed herein. In some embodiments, the method further comprises administering a therapeutically effective amount of one or more additional therapeutic agents to the subject at the same time as, or following administration of a polypeptide, composition, or pharmaceutical composition disclosed herein.

Non-limiting examples of additional therapeutic agents include antibiotics (e.g., azithromycin), antibodies or antigen-binding fragments thereof (e.g., other SARS-CoV-2-Spike-binding peptides), antimalarial agents (e.g., chloroquine or hydroxychloroquine), antiviral agents (e.g., favipiravir, lopinavir and/or ritonavir), cytokines (e.g., type 1 interferons such as interferon beta-1a), nucleotide analogs (e.g., remdesivir), protease inhibitors (e.g., danoprevir), Renin-Angiotensin-Aldosterone System Inhibitors (e.g., ACE2 inhibitors or angiotensin-receptor blockers (ARBs)).

In some embodiments, the antiviral agent is selected from the group consisting of amantadine, favipiravir, lopinavir, oseltamivir (Tamiflu), pleconaril, rimantadine, ritonavir, an anti-sense RNA to SARS-CoV-2, a siRNA to SARS-CoV-2, an additional anti-SARS-CoV-2 monoclonal antibody, and combinations thereof.

In some embodiments, the additional anti-SARS-CoV-2 monoclonal antibody targets the RBD of the S protein of SARS-CoV-2. In some embodiments, the additional anti-SARS-CoV-2 monoclonal antibody is a neutralizing monoclonal antibody. Non-limiting examples of anti-SARS-CoV-2 monoclonal antibodies include bamlanivimab (LY-CoV555 or LY3819253), etesevimab (LY-CoVO16 or LY3832479), casirivimab (REGN10933), and imdevimab (REGN10987). See, e.g., www.covid19treatmentguidelines.nih.gov/therapies/anti-sars-cov-2-antibody-products/anti-sars-cov-2-monoclonal-antibodies.

In some embodiments, the ACE2 inhibitor is selected from the group consisting of an RNAi to ACE2, a siRNA to ACE2, CRISPR-based inhibitor of ACE2, a soluble ACE2, a soluble ACE2 variant, an anti-ACE2 antibody, a vaccine, and combinations thereof. In some embodiments, the antibiotic is azithromycin. In some embodiments, the antimalarial agent comprises chloroquine or hydroxychloroquine. In some embodiments, the vaccine is a nucleic acid vaccine or an inactivated virus vaccine. In some embodiments, the vaccine is mrna-1273, BNT162, INO-4800, AZD1222, Ad5-nCoV, PiCoVacc, NVX-CoV2373, or a combination thereof.

Administration of the two or more therapeutic agents encompasses co-administration of the therapeutic agents in a substantially simultaneous manner, such as in a pharmaceutical combination. Alternatively, such administration encompasses co-administration in multiple containers, or separate containers (e.g., capsules, powders, and liquids) for each therapeutic agent. Such administration also encompasses use of each type of therapeutic agent in a sequential manner, either at approximately the same time or at different times. The composition described herein and the second therapeutic agent can be administered via the same administration route or via different administration routes.

In another aspect, the invention provides a method of preventing a SARS-CoV-2 infection in a subject, comprising administering to the subject an effective amount of a pharmaceutical composition comprising a pharmaceutically acceptable carrier and, wherein as an active ingredient, any one of the polypeptides or fusion proteins described herein.

In another aspect, the invention provides a method of treating a SARS-CoV-2 infection in a subject, comprising administering to the subject an effective amount of a pharmaceutical composition comprising a pharmaceutically acceptable carrier and, wherein as an active ingredient, any one of the polypeptides or fusion proteins described herein.

In another aspect, the invention provides a method of reducing viral load of SARS-CoV-2 in a subject, comprising administering to the subject an effective amount of a pharmaceutical composition comprising a pharmaceutically acceptable carrier and, wherein as an active ingredient, any one of the polypeptides or fusion proteins described herein.

In another aspect, the invention provides a method of inhibiting binding of SARS-CoV-2 to a target cell, comprising contacting the target cell an effective amount of any one of the polypeptides or fusion proteins described herein.

In another aspect, the invention provides a method of inhibiting binding of SARS-CoV-2 to a target protein on a target cell, comprising contacting the target cell an effective amount of any one of the polypeptides or fusion proteins described herein.

In another aspect, the invention provides a method of inhibiting virus mediated fusion with a target cell, comprising contacting the target cell an effective amount of any one of the polypeptides or fusion proteins described herein.

Unless otherwise defined, all terms of art, notations and other scientific terms or terminology used herein are intended to have the meanings commonly understood by those of skill in the art to which this invention pertains. In some cases, terms with commonly understood meanings are defined herein for clarity and/or for ready reference, and the inclusion of such definitions herein should not necessarily be construed to represent a substantial difference over what is generally understood in the art. It will be further understood that terms, such as those defined in commonly-used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and/or as otherwise defined herein.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

As used herein, the indefinite articles “a,” “an” and “the” should be understood to include plural reference unless the context clearly indicates otherwise.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word “comprise,” and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of, e.g., a stated integer or step or group of integers or steps, but not the exclusion of any other integer or step or group of integer or step. When used herein, the term “comprising” can be substituted with the term “containing” or “including.”

As used herein, “consisting of” excludes any element, step, or ingredient not specified in the claim element. When used herein, “consisting essentially of” does not exclude materials or steps that do not materially affect the basic and novel characteristics of the claim. Any of the terms “comprising,” “containing,” “including,” and “having,” whenever used herein in the context of an aspect or embodiment of the invention, can in some embodiments, be replaced with the term “consisting of,” or “consisting essentially of” to vary scopes of the disclosure.

As used herein, the conjunctive term “and/or” between multiple recited elements is understood as encompassing both individual and combined options. For instance, where two elements are conjoined by “and/or,” a first option refers to the applicability of the first element without the second. A second option refers to the applicability of the second element without the first. A third option refers to the applicability of the first and second elements together. Any one of these options is understood to fall within the meaning, and, therefore, satisfy the requirement of the term “and/or” as used herein. Concurrent applicability of more than one of the options is also understood to fall within the meaning, and, therefore, satisfy the requirement of the term “and/or.”

When a list is presented, unless stated otherwise, it is to be understood that each individual element of that list, and every combination of that list, is a separate embodiment. For example, a list of embodiments presented as “A, B, or C” is to be interpreted as including the embodiments, “A,” “B,” “C,” “A or B,” “A or C,” “B or C,” or “A, B, or C.”

Exemplification Example 1. Direct Binding between the Antigen-Binding Molecule and the S1 Subunit Receptor Binding Domain of SARS-Cov-2-Spike (RBD)

The molecule of interest is recombinantly expressed, purified, and quantified. An ELISA plate is coated with 1 μg/mL in PBS of commercial SARS-Cov-2 RBD overnight. The plate is then washed 3× with 200 μL of PBS-T on an automated plate washer and then blocked with 5% BSA in PBS for 1 hour at 37° C. to block non-specific binding. The plate is then washed 3× with 200 μL of PBS-T on an automated plate washer and the molecule of interest is titrated in a dilution series in the ELISA plate and incubated for 1 hour at 37° C. The plate is then washed 3× with 200 μL of PBS-T on an automated plate washer and a secondary antibody (conjugated with HRP) specific to the target molecule is added a fixed dilution to the plate. The plate is incubated for 1 hour at 37° C. The plate is then washed 3× with 200 μL of PBS-T on an automated plate washer and binding is probed with by adding TMB substrate to the wells of interest. After 5-10 minutes, the reaction is stopped with an acidic stop solution and the signal is quantified by measuring absorbance at 450 nm on a plate reader. A positive signal corresponds to an absorbance reading about background for a negative control (typically an antibody isotope control). A semi-quantitative understanding of the binding can be inferred by assessing strength of binding at greater dilutions of the target molecule. In theory, candidate molecules with greater affinity to the SARS-Cov-2 RBD should show greater signal at greater dilutions compared to weaker binders.

Example 2. The Antigen-Binding Molecule Competes with Human ACE2 (hACE2) for Binding to RBD In Vitro

The molecule of interest is recombinantly expressed, purified, and quantified. An ELISA plate is coated with 1 μg/mL in PBS of commercial SARS-Cov-2 RBD overnight. The plate is then washed 3× with 200 μL of PBS-T on an automated plate washer and then blocked with 5% BSA in PBS for 1 hour at 37° C. to block non-specific binding. The plate is then washed 3× with 200 μL of PBS-T on an automated plate washer and the molecule of interest is titrated in a dilution series in the ELISA plate. At the same time, a fixed concentration of commercial hACE2 (biotinylated) is co-incubated with the candidate molecule. The fixed concentration of hACE2 corresponds to the concentration at which 50% of maximal binding to SARS-Cov-2 RBD determined empirically in this assay format. The plate is incubated for 1 hour at 37° C. The plate is then washed 3× with 200 μL of PBS-T on an automated plate washer and a secondary antibody (streptavidin conjugated with HRP) specific to the biotinylated hACE2 is added a fixed dilution to the plate. The plate is incubated for 1 hour at 37° C. The plate is then washed 3× with 200 μL of PBS-T on an automated plate washer and binding is probed with by adding TMB substrate to the wells of interest. After 5-10 minutes, the reaction is stopped with an acidic stop solution and the signal is quantified by measuring absorbance at 450 nm on a plate reader. A positive signal corresponds to a decrease in absorbance for wells with the candidate molecule compared to wells without the candidate molecule above background for a negative control (typically an antibody isotope control). A semi-quantitative understanding of the target molecule's ability to compete with hACE2 can be inferred by assessing total decrease of hACE2 binding at greater dilutions of the target molecule. In theory, candidate molecules with greater ability to compete with hACE2 for SARS-Cov-2 RBD should show greater signal at greater dilutions compared to molecules with weaker ability.

Example 3. The Antigen-Binding Molecule Competes with hACE2 for Binding to RBD on Cell Surface

The molecule of interest is recombinantly expressed, purified, and quantified. A cell line expressing hACE2 at wild-type levels is cultured, harvested without trypsinization (to prevent surface protein destruction), and counted. A fixed number of cells are added to a 96 well plate and incubated with the molecule of interest titrated in a dilution series. At the same time, a fixed concentration of commercial SARS-Cov-2 (biotinylated) is co-incubated with the candidate molecule. The fixed concentration of SARS-Cov-2 corresponds to the concentration at which 50% of maximal binding to hACE2 on the cell determined empirically in this assay format. The plate of cells is incubated for 1 hour at 4° C. in the dark. The plate is centrifuged at 400×g for 5 minutes, the supernatant is aspirated, and the cells washed with 0.2% BSA in PBS. This process is repeated 2 more times for a total of 3 washes. A secondary antibody (streptavidin conjugated with Alexa Fluor 488) specific to the biotinylated SARS-Cov-2 is added a fixed dilution to the plate. The plate of cells is incubated for 1 hour at 4° C. in the dark. The plate is centrifuged at 400×g for 5 minutes, the supernatant is aspirated, and the cells washed with 0.2% BSA in PBS. The cells are then resuspended in a fixed volume of 0.2% BSA in PBS and subjected to flow cytometry. Total binding of the SARS-Cov-2 RBD is analyzed by median fluorescence intensity (MFI) of the FIT-C channel. A positive signal corresponds to a decrease in MFI for wells with the candidate molecule compared to wells without the candidate molecule above background for a negative control (typically an antibody isotope control). A semi-quantitative understanding of the ability to compete with SARS-Cov-2 RBD can be inferred by assessing total decrease of SARS-Cov-2 RBD MFI at greater dilutions of the target molecule. In theory, candidate molecules with greater ability to compete with the SARS-Cov-2 RBD for hACE2 (which can also be considered the affinity for SARS-Cov-2 RBD) should show greater signal at greater dilutions molecules with weaker ability.

Example 4. Yeast Display Characterization of Antibody Designs

Antibodies were formatted as single chain variable fragments (scFv) and tested for binding using yeast display. ScFv constructs fused to a c-myc epitope tag were synthesized as DNA fragments (TWIST Biosciences), with overhangs for cloning into a yeast display vector. DNA insert and digested vector were transformed into yeast, and the full plasmid was generated in vivo by homologous recombination. Cells were induced for scFv expression and display on the yeast cell surface. Induced cells were stained for binding to biotinylated SARS-CoV-2 receptor binding domain (RBD) antigen (Acro Biosystems) or SARS-CoV RBD (Genscript) and anti-c-myc (Exalpha) for scFv expression. For clones that showed binding, the equilibrium dissociation constant (KD) was evaluated by performing a titration curve with various concentrations of SARS-CoV-2 RBD or SARS-CoV antigen. All clones that bound SAR-CoV-2 RBD also demonstrated cross-reactive binding to SARS-CoV RBD. Binding specificity and KD values are summarized in Table 2.

Example 5. Production of Full-Length IgG

ScFv constructs were reformatted into full-length human immunoglobulin 1 (IgG1) by subcloning the variable heavy (V_(H)) chain and variable light (V_(L)) chains into mammalian expression vectors containing corresponding constant regions using conventional methods. The antibodies were generated by using one expression plasmid per chain, containing CMV promoter to drive expression and a signal peptide to promote secretion of the fully folded IgG into the supernatant. Mammalian expression host systems (such as the Chinese hamster ovary—CHO S cell line) were employed for protein expression using cationic lipid-based transient transfection methodologies with fed-batch production procedures. The expressed, soluble full length IgGs were purified using an affinity capture-based purification method using Protein A affinity resin (such as the MabSelect Sure resin, GE Healthcare) and aqueous buffers. Elution was performed under acidic conditions with low pH (such as pH 3.5) and then neutralized to pH7.5 using 2M Tris base. The purified antibodies were further stabilized in aqueous buffers (such as Histidine-based buffers containing NaCl) for long-term storage/freezing.

Example 6. Binding Kinetics and Affinity of Full-Length IgG

Binding kinetics and affinity were measured with Bio-layer interferometry (BLI) using a ForteBio Octet Red96e instrument. Antibodies were captured onto anti-human Fc (AHC) biosensors. Biosensors were then incubated with a serial dilution of SARS-CoV-2 RBD (Acro Biosystems) for association and dissociation. Representative data are shown in Table 3.

Example 7. Material and Methods

Expression of Full-Length IgG

Back-translated DNA coding for the V_(H) and V_(L) sequences of designed antibodies were synthesized (Twist) and cloned into human G1+K conta isotype vectors containing a CMV promoter sequence, signal peptide, and corresponding constant regions using Golden Gate Assembly (New England Biolabs, Ipswich, Mass.). IgG proteins were expressed in ExpiCHO cells following manufacturer's methods (Thermo Fisher Scientific, Inc., Waltham, Mass.) and purified by affinity chromatography using MabSelect Sure Protein A affinity resin (Cytiva, Marlborough, MA) per manufacturer's methods. Following Protein A affinity purification, the antibodies were further purified by size exclusion chromatography using Superdex200 resin (Cytiva, Marlborough, MA) following manufacturer's recommended methods.

Neutralization Assay

Pre-titrated amounts of rVSV-SARS-CoV-2 were incubated with serially diluted monoclonal antibodies at 37° C. for 1 hour before addition to confluent Vero (ATCC CCL-81) monolayers in 96-well plates. Infection proceeded for 16-18 hours at 37° C. in 5% CO2 before cells were fixed in 4% paraformaldehyde and stained with 10 μg/mL Hoechst. Cells were imaged using a CellInsight CX5 imager and infection was quantified by automated enumeration of total cells and those expressing green fluorescent protein (GFP). Infection was normalized to the average number of cells infected with rVSV-SARS-CoV-2 incubated with human IgG isotype control.

Generation of WT and Mutant SARS-CoV-2 Spike Proteins

Spike proteins were generated for epitope binning studies and structural biology using the HexaPro background (containing residues 14-1208 (Genbank: MN908947) of the ectodomain, six proline substitutions (F817P, A892P, A899P, A942P, K986P, V987P), as well as the D614G mutation established in all/most variants associated with spillover/spillback in Northern Europe, and replacement of cleavage site residues 682-685 (“RRAR” (SEQ ID NO: 53) to “GSAS” (SEQ ID NO: 54)). The resulting spike variants were cloned into a phCMV mammalian expression vector containing an N-terminal Gaussia luciferase signal sequence (MGVKVLFALICIAVAEA (SEQ ID NO: 55)) and a C-terminal foldon trimerization domain, followed by an HRV-3C cleavage site and a Twin-Strep-Tag. Plasmids were transformed into Stellar competent cells and isolated using a Plasmid Plus Midi kit (Qiagen, Hilden, Germany).

SARS-CoV-2 HexaPro spike was transiently transfected into Freestyle 293-F or ExpiCHO-S cells (Thermo Fisher Scientific, Inc., Waltham, Mass.). Both cell lines were maintained and transfected according to manufacturer's protocols. Briefly, 293-F cells were grown to a density of 2.0×10⁶ cells/mL and diluted to 1.0×10⁶ cell/mL on the day of transfection (day 0). Plasmid DNA and polyethyleneimine were mixed in Opti-MEM (Thermo Fisher Scientific, Inc., Waltham, Mass.), incubated for 25 minutes, and then added to the cells. Cell cultures were incubated at 37° C., 8% CO2, and 120 RPM, and harvested on day 5. For ExpiCHO cultures, manufacturer's “High Titer” protocol was used. Briefly, cells were grown to a density of 1×10⁷ cells/mL and diluted to 6×10⁶ cells/mL on the day of transfection (day 0). Plasmid DNA and Expifectamine were mixed in Opti-PRO SFM (Thermo Fisher Scientific, Inc., Waltham, Mass.) according to manufacturer's instructions, and added to the cells. On day 1, cells were fed with manufacturer-supplied feed and enhancer according to the suggested protocol, and cultures were then incubated at 32° C., 5% CO2 and 115 RPM. ExpiCHO cultures were harvested on day 7. All cultures were clarified by centrifugation, followed by addition of BioLock (IBA Lifesciences, Gottingen, Germany), and supernatants were flowed through a 0.22 μM sterile filter and purified on an Å KTA GO (Cytiva, Marlborough, MA) using a 5 mL StrepTrap-HP column equilibrated with TBS buffer (25 mM Tris pH 7.6, 200 mM NaCl, 0.02% NaN3), and eluted in TBS buffer supplemented with 5 mM d-desthiobiotin (Sigma-Aldrich, St. Louis, Mo.). The strep-tags were cleaved using HRV-3C protease and the proteins were further purified by size-exclusion-chromatography (SEC) on a Superdex 6 increase 10/300 column (GE Healthcare, Chicago, Ill.) in TBS.

High-throughput Surface Plasmon Resonance (HT-SPR) Epitope Binning

Epitope binning was performed with a sandwich assay format on a Carterra LSA SPR instrument equipped with a CMDP sensor chip at 25° C. and in a HBSTE-BSA running buffer (10 mM HEPES pH 7.4, 150 mM NaCl, 3 mM EDTA, 0.05% Tween-20, supplemented with 0.5 mg/ml BSA). Two microfluidic modules, a 96-channel print-head (96PH) and a single flow cell (SFC), were used to deliver samples onto the sensor chip. Surface preparation was performed with 25 mM MES (pH 5.5) with 0.05% Tween-20 as a running buffer. The chip was activated with a freshly prepared solution of 130 mM 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC)+33 mM N-hydroxysulfosuccinimide (Sulfo-NHS) in 0.1 M MES (pH 5.5) using the SFC. Antibodies were immobilized using the 96PH for 10 minutes at 10 μg/mL diluted into 10 mM sodium acetate (pH 4.25). Unreactive esters were quenched with a 7-minute injection of 1 M ethanolamine-HCl (pH 8.5) using the SFC. The binning analysis was performed over this array with the HBSTE-BSA buffer as the running buffer and sample diluent. The RBD antigen was injected in each cycle for 4 minutes at 50 nM (1.3 μg/mL) and followed immediately by a 4-minute injection of the analyte antibody at 30 μg/mL (200 nM for IgG constructs). The surface was regenerated each cycle with double pulses (17 seconds per pulse) of 10 mM Glycine (pH 2.0). The data was processed and analyzed with Epitope Tool software (Carterra, Salt Lake City, Utah).

Octet Affinity Measurements

Binding kinetics and affinity were measured with Bio-layer interferometry (BLI) using a ForteBio Octet Red96e instrument. Antibodies were normalized to 100 nM in 1×Kinetics Buffers and captured onto anti-human Fc (AHC) biosensors. Biosensors were then incubated with a serial dilution of SARS-CoV-2 RBD (ACROBiosystems, Newark, Del.) for determining association and dissociation rate.

Humanization of Reference Antibody-derived Sequences

Because the Reference Antibody-derived antibodies were generated based on an anti-CoV1 murine antibody, the resulting sequences harbored murine frameworks. Selected antibodies with desired binding properties were subjected to a humanization procedure, whereby their CDR fragments were transferred onto human frameworks.

More specifically, a computational approach was used to assess the compatibility between desired CDR sequences and a database of therapeutically validated human frameworks. Upon identification of these optimal frameworks, the algorithm next proposed adjustments to framework and, if necessary, some CDR positions to further improve the compatibility. Corresponding humanized antibodies were produced and characterized, e.g., for their binding affinities and kinetic properties.

Example 8. IgG1 molecules neutralize SARS-COV-2 in vitro

Nine IgG1 Abs were submitted to the Coronavirus Immunotherapy Consortium for neutralization studies. All nine IgG1 molecules show ability to block infection of Vero monolayers of both pseudo and authentic WT virus. (Table 4).

One antibody, AB-8 was chosen for further studies to determine susceptibility of emerging mutations in COV-2 RBD. Pseudovirus neutralization studies were performed with pseudovirus bearing point mutations found in multiple human and mink variants. As shown in FIG. 5 , AB-8 was resistant to most mutations, as indicated by IC50fold-change between−2.5 and 2.5.

Example 9. Epitope and Affinities

The affinities of the monoclonal antibodies against the soluble G614 HexaPro spike ectodomain and monomeric RBD were examined. Using a high-throughput surface plasmon resonance analysis, the antibodies that react with the RBD were sorted into 11 different “communities.” RBD communities were defined as the inability between two members of the same community to make SPR sandwich pairs, indicating a shared epitope for binding. It was found that AB-1 to AB-9 cluster into “RBD Community 5,” a distinct “RBD community” epitope bin (data not shown). As shown in Table 4, these antibodies show nM affinity to the target antigen, G614 HexaPro spike ectodomain or monomeric RBD.

Example 10. Humanization of IgG1 polypeptides

Select clones were further humanized using computational approaches outlined in Material and Methods. To confirm that humanization did not abolish affinity or propensity to bind COV-2 RBD, biolayer interferometry was used to assess the affinities of the newly humanized sequences against the parental “seeds.” As outlined in FIGS. 6 and 7 , humanization of the clones did not remove original seed sequence' ability to bind COV-2 RBD. Octet kinetic data are summarized in Table 5.

TABLE 1 Amino Acid Sequences Name SEQ ID Amino Acid Sequence V_(H) Consensus NO: 2 EVQLEESGTVLARPGASVKMSCKASGYTFTX₁YX₂MHWIKQRPGQ A GLEWIGAIYPGNX₃DTX₄YNQKFKDKAKLTAVX₅STSSAYMELSSL TNEDSAVYFCTREGIPQX₆X₇X₈X₉X₁₀DX₁₁WGQGTSVTVSS Reference NO: 3 EVQLEESGTVLARPGASVKMSCKASGYTFTTYRMHWIKQRPGQG LEWIGAIYPGNSDTTYNQKFKDKAKLTAVTSTSSAYMELSSLTNE DSAVYFCTREGIPQLLRTLDYWGQGTSVTVSS AB-1 NO: 4 EVQLEESGTVLARPGASVKMSCKASGYTFTTYWMHWIKQRPGQ GLEWIGAIYPGNSDTQYNQKFKDKAKLTAVKSTSSAYMELSSLTN EDSAVYFCTREGIPQLLRTLDYWGQGTSVTVSS AB-2 NO: 5 EVQLEESGTVLARPGASVKMSCKASGYTFTTYWMHWIKQRPGQ GLEWIGAIYPGNGDTNYNQKFKDKAKLTAVKSTSSAYMELSSLT NEDSAVYFCTREGIPQLLRTLDYWGQGTSVTVSS AB-3 NO: 6 EVQLEESGTVLARPGASVKMSCKASGYTFTTYWMHWIKQRPGQ GLEWIGAIYPGNGDTNYNQKFKDKAKLTAVKSTSSAYMELSSLT NEDSAVYFCTREGIPQKLRTLDVWGQGTSVTVSS AB-4 NO: 7 EVQLEESGTVLARPGASVKMSCKASGYTFTTYWMHWIKQRPGQ GLEWIGAIYPGNGDTNYNQKFKDKAKLTAVKSTSSAYMELSSLT NEDSAVYFCTREGIPQLLRTFDYWGQGTSVTVSS AB-5 NO: 8 EVQLEESGTVLARPGASVKMSCKASGYTFTSYWMHWIKQRPGQ GLEWIGAIYPGNGDTNYNQKFKDKAKLTAVKSTSSAYMELSSLT NEDSAVYFCTREGIPQLLNTLDVWGQGTSVTVSS AB-6 NO: 9 EVQLEESGTVLARPGASVKMSCKASGYTFTSYWMHWIKQRPGQ GLEWIGAIYPGNSDTNYNQKFKDKAKLTAVKSTSSAYMELSSLTN EDSAVYFCTREGIPQLTRTLDYWGQGTSVTVSS AB-7 NO: 10 EVQLEESGTVLARPGASVKMSCKASGYTFTSYWMHWIKQRPGQ GLEWIGAIYPGNSDTNYNQKFKDKAKLTAVKSTSSAYMELSSLTN EDSAVYFCTREGIPQLLRSLDYWGQGTSVTVSS AB-8 NO: 41 EVQLEESGTVLARPGASVKMSCKASGYTFTTYWMHWIKQRPGQ GLEWIGAIYPGNSDTIYNQKFKDKAKLTAVKSTSSAYMELSSLTN EDSAVYFCTREGIPQLLRTLDYWGQGTSVTVSS AB-9 NO: 42 EVQLEESGTVLARPGASVKMSCKASGYTFTSYWMHWIKQRPGQ GLEWIGAIYPGNSDTNYNQKFKDKAKLTAVTSTSSAYMELSSLTN EDSAVYFCTREGIPQLLRTLDYWGQGTSVTVSS AB-10 NO: 43 QVQLVQSGAEVKKPGASVKVSCKASGYTFTSYWMHWVRQAPG QGLEWMGAIYPGNGDTNYAQKFQGRVTMTADTSISTAYMELSRL RSDDTAVYYCTREGIPQLLNTLDVWGQGTLVTVSS AB-11 NO: 44 EVQLVQSGAEVKKSGESLKISCKASGYTFTTYWMHWVRQMPGK GLEWMGAIYPGNSDTQYSPSFQGQVTLSADKSISTAYLQWSSLKA SDTAMYFCTREGIPQLLRTLDYWGQGTLVTVSS AB-12 NO: 45 EVQLVQSGAEVKKPGESLKISCKASGYTFTTYWMHWVRQMPGK GLEWMGAIYPGNSDTRYSPSFQGQVTLSVDKSITTAYLQWNSLK ASDTAMYFCTREGIPQLLRTLDYWGQGTLVTVSS Consensus NO: 46 X₁VQLVQSGAEVKKX₂GX₃SX₄KX₅SCKASGYTFTX₆YWMHWVRQ B X₇PGX₈GLEWMGAIYPGNX₉DTX₁₀YX₁₁X₁₂X₁₃FQGX₁₄VTX₁₅X₁₆X₁₇D X₁₈SIX₁₉TAYX₂₀X₂₁X₂₂X₂₃X₂₄LX₂₅X₂₆X₂₇DTAX₂₈YX₂₉CTREGIPQLL X₃₀TLDX₃₁WGQGTLVTVSS V_(L) Consensus NO: 11 DILMTQSPSSLSASLGERVSLTCRASQEIX12GYLSWLQEKPDGTIK A RLIYAASTLDSGVPKRFSGSRSGSDYSLTISSLESEDFADYYCX₁₃Q YX₁₄SYPWTFGGGTKLEIK Reference NO: 12 DILMTQSPSSLSASLGERVSLTCRASQEISGYLSWLQEKPDGTIKRL IYAASTLDSGVPKRFSGSRSGSDYSLTISSLESEDFADYYCLQYVS YPWTFGGGTKLEIK AB-1-3, NO: 13 DILMTQSPSSLSASLGERVSLTCRASQEISGYLSWLQEKPDGTIKRL 6-9 IYAASTLDSGVPKRFSGSRSGSDYSLTISSLESEDFADYYCLQYLSY PWTFGGGTKLEIK AB-4 NO: 14 DILMTQSPSSLSASLGERVSLTCRASQEIGGYLSWLQEKPDGTIKR LIYAASTLDSGVPKRFSGSRSGSDYSLTISSLESEDFADYYCLQYLS YPWTFGGGTKLEIK AB-5 NO: 15 DILMTQSPSSLSASLGERVSLTCRASQEISGYLSWLQEKPDGTIKRL IYAASTLDSGVPKRFSGSRSGSDYSLTISSLESEDFADYYCQQYLS YPWTFGGGTKLEIK AB-10 NO: 47 DIQMTQSPSSLSASVGDRVTITCRASQEISGYLNWYQQKPGKAPK RLIYAASSLQSGVPSRFSGSGSGTDFTLTISSLQPEDFATYYCQQYL SYPWTFGQGTKVEIK AB-11 NO: 48 EIVLTQSPGTLSLSPGERATLSCRASQEISGYLAWLQQKPGQAPRR LIYAASSLATGIPDRFSGSGSGTDFTLTISRLEPEDFAVYYCLQYLS YPWTFGQGTKVEIK AB-12 NO: 49 DIQMTQSPSSLSASVGDRVTITCRASQGISGYLSWLQQKPEKAPKR LIYAASTLQSGVPSRFSGSGSGTDFTLTISSLQPEDFATYYCQQYLS YPWTFGQGTKLEIK Consensus NO: 50 X₃₂IX₃₃X₃₄TQSPX₃₅X₃₆LSX₃₇SX₃₈GX₃₉RX₄₀TX₄₁X₄₂CRASQX₄₃ISGYL B X₄₄ WX₄₅QQKPX₄₆X₄₇APX₄₈RLIYAASX₄₉LX₅₀X₅₁GX₅₂PX₅₃RFSGSGS GTDFTLTISX₅₄LX₅₅PEDFAX₅₆YYCX₅₇QYLSYPWTFGQGTKX₅₈EIK HCDR1 Consensus NO: 16 GYTFTX₁YX₂ Reference NO: 17 GYTFTTYR AB-1-4, 8, NO: 18 GYTFTTYW 11, 12 AB-5-7, 9, NO: 19 GYTFTSYW 10 HCDR2 Consensus NO: 20 IYPGNX₃DT Reference, NO: 21 TYPGNSDT AB-1, 6-9, 11,12 AB-2-5, 10 NO: 22 TYPGNGDT HCDR3 Consensus NO: 23 TREGIPQX₆X₇X₈X₉X₁₀DX₁₁ Reference, NO: 24 TREGIPQLLRTLDY AB-1, 2, 8, 9, 11, 12 AB-3 NO: 25 TREGIPQKLRTLDV AB-4 NO: 26 TREGIPQLLRTFDY AB-5, 10 NO: 27 TREGIPQLLNTLDV AB-6 NO: 28 TREGIPQLTRTLDY AB-7 NO: 29 TREGIPQLLRSLDY LCDR1 Consensus NO: 30 QEIX₁₂GY Reference, NO: 31 QEISGY AB-1-3, 5-11 AB-4 NO: 32 QEIGGY AB-12 NO: 51 QGISGY LCDR2 Consensus NO: 33 AAS LCDR3 Consensus NO: 34 X₁₃QYX₁₄SYPWT Reference NO: 35 LQYVSYPWT AB-1-4, NO: 36 LQYLSYPWT 6-9,11 AB-5, 10, NO: 37 QQYLSYPWT 12 Heavy Chain (a non-limiting example) IgG1 NO: 38 ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGA LTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSN TKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMIS RTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYN STYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKG QPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQ PENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHE ALHNHYTQKSLSLSPGK Light Chain (non-limiting examples) κ NO: 39 RTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWKVDN ALQSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEVT HQGLSSPVTKSFNRGEC λ NO: 40 GQPKANPTVTLFPPSSEELQANKATLVCLISDFYPGAVTVAWKAD GSPVKAGVETTKPSKQSNNKYAASSYLSLTPEQWKSHRSYSCQV THEGSTVEKTVAPTECS

TABLE 2 Yeast display affinity measurements YSD K_(D) (nM) SARS-CoV-2 SARS-CoV Octet K_(D) Clone RBD RBD (nM) AB-1 23 + 39 AB-2 53 + + AB-3 66 + + AB-4 22 5.0 + AB-5 47 + + AB-6 45 + + AB-8 64 + + AB-9 62 + +

TABLE 3 Binding kinetics and affinity of full- length IgG for SARS-CoV-2 RBD Clone K_(D) (nM) k_(on) (1/Ms) k_(off) (1/s) AB-1 39 6.2 × 10⁴ 2.4 × 10⁻³

TABLE 4 Affinity and Neutralization of full-length IgG1 Antibodies Neutralization (ng/mL) Affinity K_(D) (M) Pseudovirus Authentic Virus D614 D614G RBD IC₅₀ IC₈₀ IC₉₀ IC₅₀ IC₈₀ AB-5 4.95E−09 2.09E−09 1.48E−07 8.25 35.2 71.1 260 2457 AB-1 7.36E−10 3.89E−10 3.42E−08 0.0782 2.6 9.56 78 543 AB-2 3.32E−09 1.69E−09 1.27E−07 9.65 35.2 760 379 3034 AB-3 4.84E−09 2.07E−09 1.77E−07 17.6 110 502 3548 11060 AB-7 5.80E−09 2.55E−09 3.86E−07 24.6 AB-8 2.91E−09 1.73E−09 1.04E−07 0.792 3.34 7.6 222 1595 AB-9 1.96E−09 1.20E−09 9.88E−08 0.824 4.14 9.95 100 627 AB-4 3.46E−09 1.14E−09 1.51E−07 AB-6 2.89E−09 6.28E−10 1.03E−07 6.15 27.2 58.4 25000 25000

TABLE 5 Binding kinetics and affinities of full-length IgG1 Antibodies Response K_(D) (M) k_(a) (1/Ms) K_(dis) (1/s) AB-10 0.1135 2.54E−08 ± 4.81E−10 1.21E+05 ± 2.01E+03 3.06E−03 ± 2.76E−05 AB-11 0.3192 3.27E−08 ± 1.25E−10 7.80E+04 ± 2.65E+02 2.55E−03 ± 4.52E−06 AB-12 0.1453 3.24E−08 ± 4.79E−10 1.13E+05 ± 1.51E+03 3.66E−03 ± 2.28E−05 AB-5 0.3152 4.13E−08 ± 2.32E−10 8.25E+04 ± 4.26E+02 3.41E−03 ± 7.54E−06 AB-1 0.3638 1.59E−08 ± 4.52E−11 7.97E+04 ± 1.63E+02 1.27E−03 ± 2.51E−06 R_(eq)/R_(max) Full R_(max) k_(obs) (1/s) R_(eq) (%) R{circumflex over ( )}2 AB-10 0.1274 ± 0.0009 1.51E−02 ± 2.29E−04 0.1016 79.8 0.8895 AB-11 0.4325 ± 0.0008 1.04E−02 ± 3.11E−05 0.3259 75.4 0.9963 AB-12  0.178 ± 0.0011 1.49E−02 ± 1.74E−04 0.1345 75.5 0.9424 AB-5 0.4487 ± 0.0013 1.17E−02 ± 5.01E−05 0.3175 70.8 0.9932 AB-1 0.4497 ± 0.0005 9.24E−03 ± 1.88E−05 0.3881 86.3 0.9983 Response: measured as a nm shift in the interference pattern and is proportional to the number of molecules bound to the surface of the biosensor. k_(obs): the observed rate constant reflecting the overall rate of the combined association and dissociation of the two binding partners. R_(eq) (R equilibrium): the fitted binding response value (nm shift) when the binding interaction reaches equilibrium between association and dissociation for a given analyte concentration.

REFERENCES

-   1. Baud D, et al. (2020) Real estimates of mortality following     COVID-19 infection. Lancet InfectDis.: S1473-3099(20)30195-X. doi:     10.1016/S1473-3099(20)30195-X. [Epub ahead of print]. -   2. Lindsey R. Baden and Eric J. Rubin (2020) Covid-19 —The Search     for Effective Therapy, NEngl J Med., doi: 10.1056/NEJMe2005477. -   3. Ziegler et al. (2020) SARS-CoV-2 receptor ACE2 is an     interferon-stimulated gene in human airway epithelial cells and is     detected in specific cell subsets across tissues, Cell, DOI:     10.1016/j.cell.2020.04.035 [Journal pre-proof].

The teachings of all patents, published applications and references cited herein are incorporated by reference in their entirety.

While example embodiments have been particularly shown and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the embodiments encompassed by the appended claims. 

What is claimed is:
 1. A polypeptide that specifically binds a severe acute respiratory syndrome coronavirus 2 Spike glycoprotein (SARS-CoV-2-Spike), comprising a paratope that is identical to the paratope of an antibody selected from: an antibody comprising SEQ ID NO: 4 and SEQ ID NO: 13; an antibody comprising SEQ ID NO: 5 and SEQ ID NO: 13; an antibody comprising SEQ ID NO: 6 and SEQ ID NO: 13; an antibody comprising SEQ ID NO: 7 and SEQ ID NO: 14; an antibody comprising SEQ ID NO: 8 and SEQ ID NO: 15; an antibody comprising SEQ ID NO: 9 and SEQ ID NO: 13; an antibody comprising SEQ ID NO: 10 and SEQ ID NO: 13; an antibody comprising SEQ ID NO: 41 and SEQ ID NO: 13; an antibody comprising SEQ ID NO: 42 and SEQ ID NO: 13; an antibody comprising SEQ ID NO: 43 and SEQ ID NO: 47; an antibody comprising SEQ ID NO: 44 and SEQ ID NO: 48; or an antibody comprising SEQ ID NO: 45 and SEQ ID NO:
 49. 2. A polypeptide that specifically binds a severe acute respiratory syndrome coronavirus 2 Spike glycoprotein (SARS-CoV-2-Spike), comprising: a) an immunoglobulin heavy chain variable region (V_(H)) comprising a heavy chain complementarity determining region 1 (HCDR1), a heavy chain complementarity determining region 2 (HCDR2) and a heavy chain complementarity determining region 3 (HCDR3) that are identical to the HCDR1, HCDR2 and HCDR3, respectively, of SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 41, SEQ ID NO: 42, SEQ ID NO: 43, SEQ ID NO: 44 or SEQ ID NO: 45; and b) an immunoglobulin light chain variable region (V_(L)) comprising a light chain complementarity determining region 1 (LCDR1), a light chain complementarity determining region 2 (LCDR2) and a light chain complementarity determining region 3 (LCDR3) that are identical to the LCDR1, LCDR2 and LCDR3, respectively, of SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 47, SEQ ID NO: 48 or SEQ ID NO:
 49. 3. The polypeptide of claim 2, comprising the HCDR1, HCDR2 and HCDR3, and LCDR1, LCDR2 and LCDR3, of an antibody selected from: an antibody comprising SEQ ID NO: 4 and SEQ ID NO: 13; an antibody comprising SEQ ID NO: 5 and SEQ ID NO: 13; an antibody comprising SEQ ID NO: 6 and SEQ ID NO: 13; an antibody comprising SEQ ID NO: 7 and SEQ ID NO: 14; an antibody comprising SEQ ID NO: 8 and SEQ ID NO: 15; an antibody comprising SEQ ID NO: 9 and SEQ ID NO: 13; an antibody comprising SEQ ID NO: 10 and SEQ ID NO: 13; an antibody comprising SEQ ID NO: 41 and SEQ ID NO: 13; an antibody comprising SEQ ID NO: 42 and SEQ ID NO: 13; an antibody comprising SEQ ID NO: 43 and SEQ ID NO: 47; an antibody comprising SEQ ID NO: 44 and SEQ ID NO: 48; or an antibody comprising SEQ ID NO: 45 and SEQ ID NO:
 49. 4. A polypeptide that specifically binds a severe acute respiratory syndrome coronavirus 2 Spike glycoprotein (SARS-CoV-2-Spike), comprising an immunoglobulin heavy chain variable region (V_(H)) comprising SEQ ID NO: 2, wherein: X₁ is T or S; X₂ is R or W; X₃ is S or G; X₄ is T, Q or N; X₅ is T or K; X₆ is L or K; X₇is L or T; X₈is R or N; X₉ is T or S; X₁₀ is L or F; or X₁₁ is Y or V, or any combination of the foregoing.
 5. The polypeptide of claim 4, wherein: X₁ is S; X₂ is W; X₃ is G; X₄ is Q or N; X₅is K; X₆is K; X₇ is T; X₈ is N; X₉ is S; X₁₀ is F; or X₁₁ is V, or any combination of the foregoing.
 6. The polypeptide of claim 4, further comprising an immunoglobulin light chain variable region (V_(L)) comprising SEQ ID NO: 11, wherein: X₁₂ is S or G; X₁₃ is L or Q; or X₁₄ is V or L, or any combination of the foregoing.
 7. The polypeptide of claim 6, wherein: X₁₂ is G; X₁₃ is Q; or X₁₄is L, or any combination of the foregoing.
 8. The polypeptide of claim 4, wherein the V_(H) comprises a heavy chain complementarity determining region 1 (HCDR1), a heavy chain complementarity determining region 2 (HCDR2) and a heavy chain complementarity determining region 3 (HCDR3) that are identical to the HCDR1, HCDR2 and HCDR3, respectively, of SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 41 or SEQ ID NO:
 42. 9. The polypeptide of claim 8, wherein the V_(L) comprises a light chain complementarity determining region 1 (LCDR1), light chain complementarity determining region 2 (LCDR2) and light chain complementarity determining region 3 (LCDR3) that are identical to the LCDR1, LCDR2 and LCDR3, respectively, of SEQ ID NO: 13, SEQ ID NO: 14 or SEQ ID NO:
 15. 10. A polypeptide that specifically binds a severe acute respiratory syndrome coronavirus 2 Spike glycoprotein (SARS-CoV-2-Spike), comprising an immunoglobulin heavy chain variable region (V_(H)) comprising SEQ ID NO: 46, wherein: X₁ is E or Q; X₂ is P or S; X₃ is A or E; X₄ is L or V; X₅is I or V; X₆ is S or T; X₇ is A or M; X₈is K or Q; X₉ is G or S; X₁₀ is N, Q or R; X₁₁ is A or S; X₁₂ is P or Q; X₁₃ is K or S; X₁₄is Q or R; X₁₅is L or M; X₁₆ is S or T; X₁₇ is A or V; X₁₈ is K or T; X₁₉ is S or T; X₂₀ is L or M; X₂₁ is E or Q; X₂₂ is L or W; X₂₃ is N or S; X₂₄ is R or S; X₂₅ is K or R; X₂₆ is A or S; X₂₇ is D or S; X₂₈ is M or V; X₂₉ is F or Y; X₃₀ is N or R; or X₃₁ is V or Y, or any combination of the foregoing.
 11. The polypeptide of claim 10, further comprising an immunoglobulin light chain variable region (V_(L)) comprising SEQ ID NO: 50, wherein: X₃₂ is D or E; X₃₃is Q or V; X₃₄ is L or M; X₃₅ is G or S; X₃₆ is S or T; X₃₇ is A or L; X₃₈ is P or V; X₃₉ is D or E; X₄₀ is A or V; X₄₁ is I or L; X₄₂ is S or T; X₄₃ is E or G; X₄₄ is A, N or S; X₄₅ is L or Y; X₄₆ is E or G; X₄₇ is K or Q; X₄₈is K or R; X₄₉ is S or T; X₅₀ is A or Q; X₅₁ is S or T; X₅₂ is I or V; X₅₃ is D or S; X₅₄ is R or S; X₅₅ is E or Q; X₅₆ is T or V; X₅₇ is L or Q; or X₅₈ is L or V, or any combination of the foregoing.
 12. The polypeptide of claim 2, wherein: a) the V_(H) comprises SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 41 or SEQ ID NO: 42; and b) the V_(L) comprises SEQ ID NO:
 13. 13. The polypeptide of claim 2, wherein: a) the V_(H) comprises SEQ ID NO: 7; and b) the V_(L) comprises SEQ ID NO:
 14. 14. The polypeptide of claim 2, wherein: a) the V_(H) comprises SEQ ID NO: 8; and b) the V_(L) comprises SEQ ID NO:
 15. 15. The polypeptide of claim 2, wherein: a) the V_(H) comprises SEQ ID NO: 43; and b) the V_(L) comprises SEQ ID NO:
 47. 16. The polypeptide of claim 2, wherein: a) the V_(H) comprises SEQ ID NO: 44; and b) the V_(L) comprises SEQ ID NO:
 48. 17. The polypeptide of claim 2, wherein: a) the V_(H) comprises SEQ ID NO: 45; and b) the V_(L) comprises SEQ ID NO:
 49. 18. The polypeptide of claim 2, wherein the V_(H) and V_(L) are humanized, contain human framework regions, or a combination thereof.
 19. The polypeptide of claim 2, wherein the polypeptide is an antibody or an antigen-binding fragment thereof.
 20. The polypeptide of claim 19, wherein the antigen binding fragment is selected from Fab, F(ab′)₂, Fab′, scFv, or Fv.
 21. The polypeptide of claim 19, further comprising an antibody heavy chain constant region sequence, an antibody light chain constant region sequence, or both an antibody heavy chain constant region sequence and an antibody light chain constant region sequence.
 22. The polypeptide of claim 21, wherein the antibody heavy chain constant region is selected from the group consisting of an IgA constant region, an IgD constant region, an IgE constant region, an IgG constant region and an IgM constant region.
 23. The polypeptide of claim 22, wherein the antibody heavy chain constant region is an IgG1 heavy chain constant region.
 24. A fusion protein comprising the polypeptide of claim
 2. 25. A polynucleotide comprising a sequence encoding the polypeptide of claim
 2. 26. An expression vector comprising the polynucleotide of claim
 25. 27. A host cell comprising the polynucleotide of claim
 25. 28. A composition comprising the polypeptide of claim 2 and one or more pharmaceutical excipients, diluents, or carriers.
 29. A method of treating a subject in need thereof, comprising administering an effective amount of the composition of claim 28 to the subject.
 30. A method of inhibiting fusion between SARS-CoV-2-Spike and a cell in a subject, comprising contacting the cell with an effective amount of the composition of claim
 28. 